Geometric parameter optimization design method for gear with large contact ratio

Abstract

The invention relates to a geometric parameter optimization design method for a large-overlap-ratio gear, and belongs to the field of vehicle transmission design. According to the technical scheme, the geometric parameter optimization design method for the large-overlap-ratio gear comprises the following steps that S1, initial parameters of a gear pair are determined according to the speed ratio requirement and the center distance; s2, dense tooth optimization is carried out according to the tooth root strengthening effect; s3, the addendum circle is determined according to the requirement of the sliding rate # imgabs0 #; s4, distributing tooth thickness according to fatigue life and backlash requirements; s5, determining a dedendum circle according to a top clearance requirement; and S6, performing tooth root transition curve optimization and hob design according to the re-determined gear parameters, and performing hobbing simulation verification. According to the scheme, gear tooth high-strength design and dense tooth optimization are achieved through a tooth root transition curve optimization method, the meshing efficiency and the transmission stability are further considered, the tooth height is controlled and optimized through the sliding rate, the tooth thickness and the backlash are distributed by balancing the fatigue strength of the paired gear, and the macroscopic geometric parameter optimization design of the gear is achieved.

Description

Technical Field

[0001] The invention relates to the field of vehicle transmission design, and in particular to a method for optimizing geometrical parameters of gears with large contact ratio. Background Art

[0002] Gears are an important part of modern transmission, especially the current automobile transmission gears, which have high speed, high power density, wide range of heavy load, high overlap, large transmission ratio, long life, high transmission efficiency and low vibration and noise, which puts extremely high demands on gear design and processing. With the increasing demand for power density, high reliability and smoothness of automobile transmission systems, higher requirements are also put forward for gear design.

[0003] The strength of gears mainly includes two aspects, one is the contact strength of the tooth surface, and the other is the bending strength of the tooth root. When the center distance and speed ratio of a pair of gears are determined, their contact strength is proportional to the number of teeth, that is, the more teeth there are, the higher the contact strength is, the greater the overlap is, and the more beneficial it is to improve vibration and noise; however, increasing the number of teeth means reducing the modulus, and the modulus is proportional to the bending strength of the tooth root, that is, the larger the modulus, the higher the bending strength of the tooth root. Therefore, if the bending strength of the gear tooth root can be improved, the bearing capacity of the gear can be further improved, and it is beneficial to improve the transmission quality.

[0004] After the gear pair parameters are determined, the optimization of the tooth root transition curve can be regarded as the process of seeking the extreme value of the function, mainly considering the curvature radius of the curve at the 30° tangent position. The larger the radius, the stronger the load-bearing capacity. Under high-speed and heavy-load conditions, the relative sliding of the gear is an important parameter affecting the meshing efficiency and tooth surface scratches. The larger the tooth height, the greater the gear sliding rate. From this perspective, the height of the gear teeth must be limited; but a large end face overlap can effectively improve the stability of the gear transmission and improve the NVH performance. Increasing the tooth height can effectively increase the end face overlap, so the larger the working tooth height of the gear, the better. Therefore, a trade-off must be made between the sliding rate and the overlap. Summary of the invention

[0005] Aiming at the current performance requirements of large-contact gears, the present invention considers both the slip rate and the high-contact ratio and proposes a parameter optimization design method for large-contact gears.

[0006] To achieve the above purpose, a method for optimizing the geometric parameters of large contact gears is proposed, which includes the following steps: S1. Determine the initial parameters of the gear pair according to the speed ratio requirements and the center distance; S2. Optimize the dense teeth according to the tooth root strengthening effect; S3. It is required to determine the top circle of the tooth; S4. Allocate the tooth thickness according to the fatigue life and side clearance requirements; S5. Determine the root circle of the tooth according to the top clearance requirements; S6. Optimize the root transition curve and design the hob according to the re-determined gear parameters, and perform hobbing simulation verification. This solution achieves high-strength design and dense tooth optimization of gear teeth through the root transition curve optimization method, further takes into account the meshing efficiency and transmission stability, optimizes the tooth height through sliding rate control, allocates tooth thickness and side clearance by balancing the fatigue strength of the mating gear, and realizes the optimization design of the macro-geometric parameters of the gear; this method can be directly applied to engineering practice to improve the quality of gear products.

[0007] As a preferred implementation scheme of the method for optimizing the geometric parameters of large contact gears, in step S1, the initial parameters of the gear pair include the rotation direction of the gear, the number of teeth of the first gear, 、Number of teeth of the second gear and normal modulus , pressure angle and helix angle : As a preferred implementation scheme for the geometric parameter optimization design method of large contact gears, S1-1. Determine the number of teeth of the first gear in the gear pair according to the transmission ratio and the center distance , Number of teeth of the second gear and normal modulus , under the premise of ensuring that the pitch diameter of the gear is constant, the dense tooth optimization is achieved by increasing the number of teeth and reducing the module, ensuring that the product of the number of teeth Z and the module m remains unchanged; S1-2. Determine the rotation direction and pressure angle of the gear according to the distribution of axial force and helix angle According to the gear top clearance requirements, the tooth root transition curve form is predetermined. Through the constraints of the tooth vertex spiral curve, working tooth profile curve and root circle of the mating gear, the detailed parameters of the tooth root curve are optimized with the goal of minimizing the tooth root bending stress, and the transition curve equation is determined.

[0008] As a preferred implementation scheme of a method for optimizing the geometric parameters of gears with large contact ratio, step S2 includes: S2-1. Maintain the gear center distance and pressure angle and helix angle No change, increase the number of teeth and / or reduce the module; S2-2. Improve the bending strength of the gear teeth by strengthening the tooth root to ensure that the bending strength of the gear teeth does not decrease after the close-pitch optimization; After the tooth density is optimized, the number of teeth on the first gear is increased to , the number of teeth of the second gear increases to , the normal modulus is reduced to .

[0009] As a preferred implementation scheme of the geometric parameter optimization design method for large contact gears, in step S3, assume that any point on the tooth profile of the first gear is M1, and the sliding rate of point M1 is :

[0010] Where: L1 is the distance from point M1 to node P when it is the meshing point, and is the pitch radius of the mating tooth, is the end face pressure angle of the gear, ; The radius of the tooth tip circle of the second gear can be obtained as : .

[0011] Similarly, the addendum circle of the first gear can be determined .

[0012] As a preferred implementation scheme of a method for optimizing the geometric parameters of gears with large contact ratio, the slip rate between the first gear and the second gear is no higher than 3%.

[0013] As a preferred implementation scheme for the geometric parameter optimization design method of gears with large overlap, when determining the tooth top circle, ensure that the tooth top thickness is less than 0.3 times the normal module. When the tooth top thickness is less than 0.3 times the normal module, give priority to ensuring the tooth top thickness.

[0014] As a preferred implementation scheme of the geometric parameter optimization design method of gears with large overlap, in step S4, the common normal length of the first gear and the second gear is determined under the conditions of side clearance and gear tooth bending fatigue strength; when the transmission ratio is greater than 3, the small gear tooth thickness is increased and the large gear tooth thickness is reduced to balance the strength.

[0015] As a preferred implementation scheme of a method for optimizing the geometric parameters of gears with large contact ratio, in step S5, the top coefficient is 0.3-0.35.

[0016] As an optimal implementation scheme for the geometric parameter optimization design method of large overlap gears, the transition curve equation is determined by directly giving the tooth root transition curve form, taking the minimum root bending stress and the product of the tooth shape coefficient Yf and the stress correction coefficient Ys as the goal, and optimizing.

[0017] It can be seen from the above technical solutions that the advantages of the present invention are as follows: This method not only realizes the high-strength design of the gear teeth through the refined optimization of the tooth root transition curve, but also greatly improves the bending fatigue strength of the gear teeth, so that the gears can maintain a longer service life while bearing a larger load. At the same time, the dense tooth optimization strategy in this solution, by carefully adjusting the tooth pitch, not only improves the meshing efficiency of the gears, but also makes the transmission more compact and optimizes the space utilization. By optimizing the tooth height through sliding rate control, the sliding friction of the gears during the meshing process is effectively reduced, the energy loss is reduced, and the wear resistance and transmission efficiency of the gears are improved. In the distribution of tooth thickness and side clearance, this method fully considers the fatigue strength balance of the paired gears, which not only ensures the smoothness of the transmission, reduces vibration and noise, but also significantly improves the fatigue life of the gears. This method has a clear design idea and clear implementation steps, and is easy to apply in engineering practice, which greatly improves the accuracy of gear design and production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0019] Figure 1 The present invention is a method flow chart of a specific implementation method.

[0020] Figure 2 This is a comparison diagram of the tooth root transition curves before and after tooth root optimization in S1 of the present invention.

[0021] Figure 3 This is a graph showing the sliding rate variation trend of the gear in S3 of the present invention.

[0022] Figure 4 It is the hob profile curve and its verification diagram in step S6 of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in this specific embodiment. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of them. Based on the embodiments in this patent, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

[0024] Embodiment 1 This embodiment provides a method for optimizing the geometric parameters of gears with a large overlap ratio. Assuming that two gears meshing with each other are a first gear and a second gear, the method includes the following steps: S1. Determine the initial parameters of the gear pair according to the speed ratio requirements and center distance: The initial parameters of the gear pair include the rotation direction of the gear, the number of teeth of the first gear 、Number of teeth of the second gear and normal modulus , pressure angle and helix angle , determine the number of teeth of the gear pair according to the transmission ratio and center distance , and normal modulus ; S1-2. Determine the rotation direction and pressure angle of the gear according to the axial force distribution and helix angle .

[0025] Specifically, under the premise of ensuring that the pitch diameter of the gear is constant, the dense gear is optimized by increasing the number of teeth and reducing the module, ensuring that the product of the number of teeth Z and the module m remains unchanged. According to the gear top clearance requirements, the predetermined tooth root transition curve form is as follows: Figure 1 Curve 1 in the figure is optimized by the constraints of the tooth vertex spiral curve, working tooth profile curve and root circle of the mating gear, with the goal of minimizing the root bending stress calculated by the ISO6336 formula to obtain the detailed parameters of the root curve and determine the transition curve equation, such as Figure 1 Curve 2 in .

[0026] S2. Optimize the close-toothed gear according to the tooth root strengthening effect, including: S2-1. Maintain the gear center distance and pressure angle and helix angle No change, increase the number of teeth and / or reduce the module; S2-2. Improve the bending strength of the gear teeth by strengthening the tooth root to ensure that the bending strength of the gear teeth does not decrease after the close-pitch optimization; S2-3. After the tooth density is optimized, the number of teeth on the first gear is increased to , the number of teeth of the second gear increases to , the normal modulus is reduced to .

[0027] S3. According to the sliding rate It is required to determine the addendum circle. Figure 2 This is the sliding rate change trend chart: Assume that any point on the first gear tooth profile is M1, and the sliding rate of point M1 is :

[0028] Where: L1 is the distance from point M1 to node P when it is the meshing point, and is the pitch radius of the mating tooth, is the end face pressure angle of the gear, ; The radius of the second gear tooth tip circle : , Similarly, the addendum circle of the first gear can be determined .

[0029] In the calculation process of S3 above, the slip rate between the first gear and the second gear is not higher than 3%.

[0030] S4. Allocate tooth thickness according to fatigue life and backlash requirements: Determine the common normal length of the first gear and the second gear under the condition of considering the side clearance and gear tooth bending fatigue strength; when the transmission ratio is large, such as the transmission ratio is greater than 3, increase the thickness of the small gear tooth and reduce the thickness of the large gear tooth to balance the strength.

[0031] S5. Determine the root circle according to the top clearance requirements: Under large end face overlap, in order to ensure sufficient lubrication, the top coefficient is often greater than the standard value of 0.25, but it cannot be too large to ensure the strength of the gear teeth. In this method, 0.3~0.35 is usually appropriate, which can ensure the effective meshing length of the tooth profile and provide space for tooth root optimization.

[0032] S6. Optimize the tooth root transition curve and design the hob according to the re-determined gear parameters, and perform hobbing simulation verification: Optimize the tooth root transition curve, that is, "tooth root strengthening", by directly giving the tooth root transition curve form, with the goal of minimizing the tooth root bending stress (the product of the tooth shape coefficient Yf and the stress correction coefficient Ys), and optimize the transition curve equation. Figure 4 It is the hob profile curve and its verification diagram.

[0033] Embodiment 2 This embodiment further provides a design method based on the first embodiment. The method is basically the same as the first embodiment and includes: S1. Determine the initial parameters of the gear pair according to the speed ratio requirements and center distance: The initial parameters of the gear pair include the rotation direction of the gear, the number of teeth of the first gear 、Number of teeth of the second gear and normal modulus , pressure angle and helix angle , determine the number of teeth of the gear pair according to the transmission ratio and center distance , and normal modulus ; S1-2. Determine the rotation direction and pressure angle of the gear according to the axial force distribution and helix angle ; S2. Optimize the close gearing according to the tooth root strengthening effect: S2-1. Maintain the gear center distance and pressure angle and helix angle The number of teeth on the first gear is increased to 100,000. , the number of teeth of the second gear increases to , the normal modulus is reduced to .

[0034] S3. According to the sliding rate It is required to determine the addendum circle, including the addendum circle of the first gear and the radius of the second gear tooth tip circle The calculation process is the same as that of Example 1: In this embodiment, the sliding rate between the first gear and the second gear is not higher than 3%. When the tooth top circle is determined, it is also necessary to prevent the gear tooth top from becoming pointed, that is, the normal tooth top thickness is less than 0.3 times the normal module. If this occurs, even if the sliding rate is less than 3%, the tooth top thickness must be guaranteed first.

[0035] S4. Allocate tooth thickness according to fatigue life and backlash requirements.

[0036] S5. Determine the root circle according to the top clearance requirements.

[0037] S6. Optimize the tooth root transition curve and design the hob based on the re-determined gear parameters.

[0038] The specific process of S4-S6 is the same as that of the first embodiment and will not be repeated here.

[0039] It can be seen from the above embodiments that the beneficial effect of the present invention is that the method not only realizes the high-strength design of the gear teeth through the refined optimization of the tooth root transition curve, but also greatly improves the bending fatigue strength of the gear teeth, so that the gears can maintain a longer service life while bearing a larger load. At the same time, the dense tooth optimization strategy in this scheme, by carefully adjusting the tooth pitch, not only improves the meshing efficiency of the gears, but also makes the transmission more compact and optimizes the space utilization. By optimizing the tooth height through the sliding rate control, the sliding friction of the gears during the meshing process is effectively reduced, the energy loss is reduced, and the wear resistance and transmission efficiency of the gears are improved. In the distribution of tooth thickness and side clearance, this method fully considers the fatigue strength balance of the paired gears, which not only ensures the smoothness of the transmission, reduces vibration and noise, but also significantly improves the fatigue life of the gears. The design idea of ​​this method is clear, the implementation steps are clear, and it is easy to apply in engineering practice, which greatly improves the accuracy of gear design and production efficiency.

[0040] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for optimizing the geometric parameters of large contact gears, characterized in that: The following steps are involved: S1. Determine the initial parameters of the gear pair according to the speed ratio requirements and center distance; S2. Optimize the close-toothed gear according to the tooth root strengthening effect; S3. According to the sliding rate It is required to determine the addendum circle; S4. Allocate tooth thickness according to fatigue life and backlash requirements; S5. Determine the root circle according to the top clearance requirements; S6. Optimize the tooth root transition curve and design the hob according to the re-determined gear parameters, and perform hobbing simulation verification.

2. The method for optimizing geometric parameters of gears with large contact ratio according to claim 1, characterized in that: In step S1, the initial parameters of the gear pair include the rotation direction of the gear, the number of teeth of the first gear, 、Number of teeth of the second gear and normal modulus , pressure angle and helix angle .

3. The method for optimizing geometric parameters of gears with large contact ratio according to claim 2, characterized in that: Step S1 includes: S1-1. Determine the number of teeth of the first gear in the gear pair based on the transmission ratio and center distance , Number of teeth of the second gear and normal modulus , under the premise of ensuring that the pitch diameter of the gear is constant, the dense gear optimization is achieved by increasing the number of teeth and reducing the module, ensuring that the product of the number of teeth Z and the module m remains unchanged; S1-2. Determine the rotation direction and pressure angle of the gear according to the axial force distribution and helix angle According to the gear top clearance requirements, the tooth root transition curve form is predetermined. Through the constraints of the tooth vertex spiral curve, working tooth profile curve and root circle of the mating gear, the detailed parameters of the tooth root curve are optimized with the goal of minimizing the tooth root bending stress, and the transition curve equation is determined.

4. The method for optimizing geometric parameters of gears with large contact ratio according to claim 2, characterized in that: Step S2 includes: S2-1. Maintain the gear center distance and pressure angle and helix angle No change, increase the number of teeth and / or reduce the module; S2-2. Improve the bending strength of the gear teeth by strengthening the tooth root to ensure that the bending strength of the gear teeth does not decrease after the close-pitch optimization; S2-3. After the tooth density is optimized, the number of teeth on the first gear is increased to , the number of teeth of the second gear increases to , the normal modulus is reduced to .

5. The method for optimizing geometric parameters of gears with large contact ratio according to claim 4 is characterized in that: Step S3 includes determining the tip circle radius: Assume that any point on the first gear tooth profile is M1, and the sliding rate of point M1 is : Where: L1 is the distance from point M1 to node P when it is the meshing point, and is the pitch radius of the mating tooth, is the end face pressure angle of the gear, ; The radius of the second gear tooth tip circle : ， Similarly, the addendum circle of the first gear can be determined .

6. The method for optimizing geometric parameters of gears with large contact ratio according to claim 5, characterized in that: In step S3, the slip rate between the first gear and the second gear is not higher than 3%.

7. The method for optimizing geometric parameters of gears with large contact ratio according to claim 6, characterized in that: Step S3 also includes determining the tooth top circle tooth thickness: ensuring that the tooth top thickness is less than 0.3 times the normal module. When the tooth top thickness is less than 0.3 times the normal module, the tooth top thickness is prioritized.

8. The method for optimizing geometric parameters of gears with large contact ratio according to claim 5, characterized in that: In step S4, the common normal lengths of the first gear and the second gear are determined under the conditions of side clearance and gear tooth bending fatigue strength; when the transmission ratio is greater than 3, the small gear tooth thickness is increased and the large gear tooth thickness is reduced to balance the strength.

9. The method for optimizing geometric parameters of gears with large contact ratio according to claim 8, characterized in that: In step S5, the top coefficient is 0.3-0.

35.

10. The method for optimizing geometric parameters of gears with large contact ratio according to claim 1, characterized in that: In step S6, by directly giving the tooth root transition curve form, with the goal of minimizing the tooth root bending stress and the product of the tooth shape coefficient Yf and the stress correction coefficient Ys, the transition curve equation is determined by optimization.

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