Variable-tooth worm and machining method thereof

Abstract

The invention relates to a variable-tooth worm and a machining method thereof, and relates to the technical field of worm structures, the variable-tooth worm comprises a shaft body and threaded teeth arranged on the shaft body, the lead of the threaded teeth is not changed along the overall length of the worm, and the tooth root surface and the tooth top surface can be cylindrical surfaces or arc revolution surfaces; threaded teeth are formed by sweeping a linear cutting edge along a space constant-lead variable-diameter spiral line, a spiral line mathematical equation is further given, related structural parameters of the threaded teeth are specifically limited, meanwhile, a machining method of the variable-tooth worm is introduced and comprises the steps of rough machining, finish machining, slotting, heat treatment, tooth grinding and the like on a blank, five-axis linkage control is adopted for a numerical control machine tool, and the machining precision of the variable-tooth worm is greatly improved. And the worm gear is meshed with the worm to form four to five pairs of continuously meshed contact areas. The technical effects that the structural design of the variable-tooth worm is optimized, the machining precision and quality are improved, and the meshing performance of the worm gear and the worm is improved are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of worm structures, and in particular to a variable-tooth worm and a processing method thereof. Background Art

[0002] In the field of mechanical transmission, conventional cylindrical worm gears are widely used due to their unique advantages. This transmission method enables large transmission ratios, typically reaching 100 for a single stage, and even exceeding 1500 in some specialized indexing mechanisms. This characteristic enables worm gears to achieve large speed changes within a small space, making them particularly suitable for applications requiring large reduction ratios.

[0003] Conventional cylindrical worm gears offer a compact structure, light size, and low weight, effectively saving installation space and making them particularly suitable for space-constrained mechanical systems. Furthermore, this transmission method offers smooth operation and low noise levels. This is because the helical teeth of the worm mesh with the worm wheel teeth in continuous line contact, eliminating the sudden engagement and disengagement seen in gear transmissions. This significantly reduces vibration and noise, making it particularly suitable for environments sensitive to noise and vibration.

[0004] Another noteworthy characteristic of ordinary cylindrical worm gears is their self-locking nature. When the worm's helix angle is very small, only the worm can drive the worm wheel, while the worm wheel cannot drive the worm in the opposite direction. This characteristic is particularly important in mechanical devices that must prevent reverse rotation, such as cranes and jacks.

[0005] However, conventional cylindrical worm gearing also has some significant drawbacks. The most prominent issue is its low efficiency. This is primarily due to the high relative sliding speed during the meshing of the worm and worm wheel, which results in high friction losses and thus affects the overall transmission efficiency.

[0006] To address the low transmission efficiency of conventional cylindrical worms, the industry has developed an enveloping worm. The tooth top and flank base circles of this worm are both concave arcs of revolution, and the large number of meshing teeth contributes to its high load capacity and transmission efficiency. However, enveloping worms also present new challenges: high thermal mass, sensitivity to center distance and axial position, and difficulty in manufacturing and inspection. These factors contribute to high manufacturing costs.

[0007] U.S. Patent No. 6176148B1 proposes an improved design: a variable-tooth worm. This worm features a cylindrical or convex top surface, with the tooth profile formed by rotating a curved line. This design offers variable tooth thickness and height. This design improves load capacity and transmission efficiency during meshing, bringing transmission performance closer to ideal. Compared to cylindrical worms, it features a greater number of simultaneously meshing teeth, and the gears can gradually enter and exit meshing. Furthermore, it offers advantages such as lower oil churning losses, a lower center distance requirement, and axial position adjustment.

[0008] Despite this, existing worm drive solutions still have some problems. First, under heavy load conditions, the load-bearing capacity of existing worms is still insufficient, unable to meet the needs of certain high-load applications. Second, the existing worm design still has certain difficulties in the manufacturing process, which not only increases production costs but also affects the precision and consistency of the product. Finally, the efficiency of existing worm drives still has room for improvement, especially during long-term operation, where energy loss remains a concern. Summary of the Invention

[0009] In order to solve the problem in the prior art that the load-bearing capacity of the existing worm is still insufficient under heavy-load conditions and cannot meet the needs of certain high-load applications, the present application provides a variable-tooth worm and a processing method thereof.

[0010] The variable tooth worm provided in the present application adopts the following technical solution: a variable tooth worm, comprising a shaft and threaded teeth arranged on the shaft, the lead of the threaded teeth remaining unchanged along the entire length of the worm, the root surface of the threaded teeth being set as a cylindrical surface or a circular arc rotation surface, and the top surface of the threaded teeth being set as a cylindrical surface or a circular arc rotation surface.

[0011] By adopting this technical solution, the root and tip surfaces of the worm's thread teeth can be cylindrical or circular surfaces. This design ensures that the thread lead remains constant along the entire length of the worm. This geometric design improves the meshing performance between the worm and the worm wheel, thereby increasing the transmission's load capacity and efficiency.

[0012] Optionally, the thread teeth are formed by sweeping a straight blade along a spatial constant lead variable diameter helix, the lead of the spatial constant lead variable diameter helix remains constant and the diameter changes with the axial position.

[0013] By adopting the above technical solution, the thread teeth are formed by a straight blade sweeping along a constant lead and variable diameter helix in space, and the lead of the helix is constant and the diameter changes with the axial position, which can ensure the constant lead and variable diameter characteristics of the thread teeth in space, thereby optimizing the geometric parameters of the thread teeth and improving the load-bearing capacity of the worm.

[0014] Optionally, the mathematical equation of the spatial constant lead variable diameter helix is: z=z1 Where z1 is obtained by solving the equation: Where: P is the helical lead, r1 is the worm pitch circle radius, r2 is the worm wheel pitch circle radius, α is the worm thread tooth profile pressure angle, and θ is the helical parameter (independent variable).

[0015] By adopting the above technical solution, the spatial constant lead variable diameter helix equation of the thread teeth is determined, which can ensure the constant lead variable diameter characteristics of the thread teeth in space, ensure the accuracy of the tooth shape, and thus improve the load-bearing capacity of the variable tooth worm.

[0016] Optionally, the tooth top surfaces at both ends of the threaded teeth are set as cylindrical surfaces, and the middle tooth top surface is set as an arc rotation surface.

[0017] By adopting the above technical solution, the thread tooth lead of the variable tooth worm remains unchanged along the overall length, the tooth root surface and the tooth top surface are cylindrical surfaces or circular arc rotation surfaces, and the tooth top surfaces at both ends are set as cylindrical surfaces and the middle is set as an arc rotation surface, which can increase the load-bearing capacity of the worm, and maintain a shape similar to that of a toroidal worm to improve the load-bearing capacity. At the same time, the tooth tops at both ends are flattened to increase the heat dissipation space, which is conducive to the formation of oil film, thereby solving the problem of high calorific value and also helping to reduce production costs.

[0018] Optionally, the number of teeth located within the circular arc rotation surface of the thread tooth top is 4-6.

[0019] By adopting the above technical solution, it can be ensured that the number of teeth participating in the meshing process at the same time is sufficient to improve the stability and efficiency of the transmission, so that the thread teeth of the variable tooth worm can be reasonably distributed while ensuring the load-bearing capacity. It is similar to the shape of the toroidal worm to improve the load-bearing capacity, and because an appropriate number of teeth are located in the tooth top arc rotating surface, the high heat value problem caused by too many teeth is avoided. There is also a larger heat dissipation space that is conducive to the formation of an oil film and is conducive to controlling the accuracy during processing. With the help of CNC machine tools, the processing of this structure can be better realized.

[0020] Optionally, the arc radius of the thread tooth top arc rotation surface is 1.04-1.11 times the radius of the matching worm gear tooth root circle.

[0021] By adopting the above technical solution, thread teeth are provided on the shaft body and the lead of the thread teeth remains unchanged along the entire length of the worm, and the root surface and the tooth top surface are set as cylindrical surfaces or circular arc rotation surfaces to ensure the basic transmission function of the worm; the arc radius of the circular arc rotation surface of the thread tooth top is set to 1.04-1.11 times the radius of the matching worm wheel tooth root circle, which can optimize the meshing of the variable tooth worm and the worm wheel, further improve the load-bearing capacity of the variable tooth worm, and enhance the stability and reliability of the variable tooth worm transmission.

[0022] Optionally, the base reference surface of the worm tooth surface is a cylindrical surface.

[0023] By adopting the above technical solution, the reference surface is a cylindrical surface, which is conducive to accurately determining the position and direction of the worm during the manufacturing and assembly process, improving the processing accuracy, enabling the variable tooth worm to better cooperate with the worm wheel, reducing friction loss and improving transmission efficiency.

[0024] A method for processing a variable tooth worm, characterized by comprising the following steps: S1. Perform rough and fine machining on the worm blank to form an external dimension reference; S2. slotting the worm blank according to the spatial constant lead variable diameter helix; S3. Tempering or quenching the slotted worm; S4, trimming the toothed grinding wheel using a CNC machine tool to form an envelope surface, and grinding along the spiral line to form thread teeth; S5. Perform gear hobbing on the worm gear blank to form a finished worm gear.

[0025] Optionally, the CNC machine tool uses five-axis linkage control to complete the trimming of the envelope surface and the grinding of the thread teeth.

[0026] Optionally, during the meshing process of the worm wheel and the worm, the tooth surface of the worm wheel and the thread teeth of the worm form four to five pairs of continuously meshing contact areas.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. This application improves the load-bearing capacity of the worm drive by adopting a variable tooth height design and a specific helical equation; 2. This application simplifies the manufacturing method of the worm, thereby reducing the manufacturing difficulty and cost; 3. This application improves transmission efficiency by optimizing tooth design and meshing method, and has the advantages of increasing load-bearing capacity, reducing manufacturing difficulty and cost, and improving transmission efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of a variable-tooth worm in an embodiment of the present application.

[0029] Figure 2 This is a schematic diagram of the relationship between the installation of the turning tool and the cutting motion in the worm turning process in the embodiment of the present application.

[0030] Description of the accompanying drawings: 1. shaft; 2. threaded teeth. DETAILED DESCRIPTION

[0031] The following describes the implementation of the present application through specific embodiments. People familiar with this technology can easily understand other advantages and effects of the present application from the contents disclosed in this specification.

[0032] See also Figure 1-2 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of this application. Therefore, they have no substantive technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed in this application without affecting the efficacy and purpose that can be achieved by this application. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of this application. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of this application without substantially changing the technical content.

[0033] The following is combined with Figure 1-2 This application is described in further detail.

[0034] Example 1 This embodiment discloses a variable-tooth worm.

[0035] Reference Figure 1 The variable tooth worm provided in the embodiment of the present application includes a shaft body and threaded teeth provided on the shaft body, wherein the shaft body serves as a mounting base for the threaded teeth and provides support for the threaded teeth. The two are tightly combined to form a variable tooth worm. Such a structure enables the variable tooth worm to stably perform transmission work, thereby improving the stability of the entire transmission system. Specifically, the shaft is generally made of metal, such as carbon steel or alloy steel, because they have good strength and toughness. The shaft is usually cylindrical, and its surface must ensure a certain degree of finish to reduce friction with other components. The shaft can also be designed into other shapes according to actual needs, such as a tapered shape to adapt to specific installation environments. When manufacturing the shaft, the general shape can be obtained through forging or rolling, and then it can be processed through turning, grinding and other processing processes to achieve the required precision. The thread teeth are formed by the straight blade sweeping along the spatial constant lead variable diameter helix. The mathematical equation of the spatial constant lead variable diameter helix is: Where z1 is obtained by solving the equation: Where: P is the helical lead, r1 is the worm pitch circle radius, r2 is the worm wheel pitch circle radius, α is the worm tooth profile pressure angle, and θ is the helical parameter (independent variable); The lead of the spatial constant-lead variable-diameter helix here remains constant, while its diameter varies with axial position. This means that the lead of the thread teeth remains constant along the entire length of the worm, but the diameter changes. This special shape design optimizes the geometric parameters of the thread teeth, thereby improving the load-bearing capacity of the worm. The root surface of the thread teeth is set as a cylindrical surface or a circular arc surface of revolution, and the tooth top surface is set as a cylindrical surface or a circular arc surface of revolution. For the tooth root surface, if it is set as a cylindrical surface, its manufacturing is relatively simple and it is more suitable for some occasions where the precision requirements are not particularly high; if it is set as an arc revolving surface, it can better disperse the stress and improve the strength of the tooth root. For example, in the case of heavy-load transmission, the tooth root surface with an arc revolving surface can effectively reduce the risk of tooth root fracture. The tooth top surface is set as a cylindrical surface or an arc revolving surface for similar reasons; the tooth top surface of the cylindrical surface is easy to process, while the tooth top surface of the arc revolving surface can better cooperate with the worm gear and improve the smoothness of the transmission; The tooth top surfaces at both ends of the thread teeth are set as cylindrical surfaces, and the tooth top surface in the middle is set as an arc-shaped rotation surface. This design allows the thread teeth to play different roles in different locations. The cylindrical tooth top surfaces at both ends facilitate installation and positioning, while the arc-shaped rotation surface in the middle can enhance the meshing effect with the worm gear and improve transmission efficiency. The number of teeth located within the arc-shaped rotation surface of the thread tooth top is 4-6. This tooth number range has been verified by extensive practice to ensure load-bearing capacity while not making the structure too complicated. The arc radius of the rotating surface of the thread tooth top arc is 1.04-1.11 times the radius of the matching worm gear tooth root circle. This proportional relationship ensures a good meshing clearance between the thread teeth and the worm gear, which not only guarantees sufficient lubrication space but also prevents transmission instability caused by excessive clearance. The base reference surface of the worm tooth surface is a cylindrical surface, which helps to determine the accurate position and size during processing and testing, thereby improving production precision and quality. The implementation principle of this embodiment is as follows: the variable tooth worm of this embodiment optimizes the geometric parameters of the worm and effectively improves the load-bearing capacity through the unique thread tooth structure design. The spatial constant lead variable diameter characteristic of the thread teeth makes the force distribution more uniform during the transmission process and reduces the problem of local stress concentration. The reasonable setting of the root surface and the tooth top surface can not only ensure sufficient strength, but also improve the smoothness and efficiency of the transmission. The design of the tooth top surfaces with different shapes at both ends and in the middle, as well as the appropriate number of teeth and the proportional relationship between the radius of the tooth top arc rotation surface and the root circle radius of the worm wheel, further enhance the meshing effect of the worm and the worm wheel. Compared with the ordinary cylindrical worm and the annular surface enveloping worm in the prior art, it has obvious advantages in terms of load-bearing capacity, transmission efficiency and cost, and solves many problems existing in the prior art.

[0036] Example 2 This embodiment differs from the previous embodiment in that the thread teeth in this embodiment are manufactured using a different process. Casting can be used to initially form the thread teeth, followed by minor machining adjustments. The casting material can be selected from alloys with excellent wear resistance, such as copper or aluminum alloys. Using a casting process can reduce production costs and is particularly suitable for large-scale production.

[0037] The operating principle of this embodiment is as follows: By modifying the manufacturing process for the thread teeth, this embodiment reduces production costs while maintaining the performance of the variable-pitch worm. The casting process enables the formation of relatively complex thread tooth shapes in a single step, reducing processing steps and time, and improving production efficiency. The use of alloy materials with excellent wear resistance ensures the stable performance of the thread teeth during long-term use, extending the service life of the variable-pitch worm. Compared with traditional processing methods, this embodiment achieves a better balance between cost and performance, further improving the existing technology.

[0038] Example 3 The method for processing a variable tooth worm provided in an embodiment of the present application comprises the following steps: S1. Rough and finish the worm blank to establish a datum for the outer dimensions. First, select a suitable metal material for the worm blank, typically carbon steel or alloy steel. Rough machining is then performed on a lathe, milling machine, or other machine tool to remove most of the excess material and establish a rough outline. Finishing is then performed, using processes such as grinding, to achieve the desired outer dimensions of the worm, providing an accurate datum for subsequent machining.

[0039] S2. Slot the worm blank according to the spatial constant lead variable diameter helix. This step requires the use of special slotting equipment, refer to Figure 2, according to the pre-set parameters of the spatial constant lead variable diameter helix, the thread groove is accurately cut on the worm blank. During the groove cutting process, it is necessary to ensure that the movement trajectory of the tool strictly conforms to the requirements of the helix to ensure the shape and dimensional accuracy of the thread teeth.

[0040] S3. Temper or quench the slotted worm. Tempering improves the worm's overall mechanical properties, imparting both high strength and good toughness. Quenching significantly increases the worm's hardness and wear resistance. The specific treatment method used depends on the worm's intended use and performance requirements.

[0041] S4. Using a CNC machine tool, the toothed grinding wheel is trimmed to form an envelope surface, which is then ground along the helical line to form the threaded teeth. The CNC machine tool can precisely control the motion trajectory and trimming parameters of the toothed grinding wheel, allowing the grinding wheel to form a desired envelope surface. The grinding wheel then grinds the worm along the spatial constant-lead, variable-diameter helical line, ultimately forming precise threaded teeth. During this process, the CNC machine tool utilizes five-axis linkage control to complete the trimming of the envelope surface and the grinding of the threaded teeth. This five-axis linkage enables more complex motion, improving machining accuracy and efficiency.

[0042] S5. Hob the worm gear blank to form the finished worm gear. A gear hobbing machine is used to process the worm gear blank. The relative motion between the hob and the worm gear blank gradually creates the worm gear tooth profile. During the machining process, the hob parameters must match those of the worm to ensure good meshing between the worm gear and the worm.

[0043] The implementation principle of this embodiment is as follows: the processing method of this embodiment can accurately manufacture variable tooth worms and worm wheels that meet the design requirements through a series of rigorous steps. From the rough and fine processing of the blank to grooving, heat treatment, and finally grinding and hobbing, each step is closely coordinated to ensure the accuracy and quality of the product. In particular, the five-axis linkage control of the CNC machine tool makes the processing more flexible and precise, and can realize the processing of complex spatial constant lead variable diameter helices. Compared with traditional processing technology, the entire processing method can better guarantee the performance of the variable tooth worm, improve production efficiency, reduce production costs, and effectively solve the problems of difficult processing and high costs in the existing technology.

[0044] The above are all preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application. The implementation principle of a variable tooth worm in this embodiment is:

[0045] In summary, this application improves the load-bearing capacity of worm gear transmissions by adopting a variable tooth height design and a specific helix equation; simplifies the worm manufacturing method, reducing manufacturing difficulty and cost; and improves transmission efficiency by optimizing the tooth profile design and meshing method. This application has the advantages of increasing load-bearing capacity, reducing manufacturing difficulty and cost, and improving transmission efficiency. Therefore, this application effectively overcomes the various shortcomings of the existing technology and has high industrial application value.

[0046] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, any equivalent modifications or alterations made by a person skilled in the art without departing from the spirit and technical concepts disclosed in this application shall be included within the scope of protection of this application.

Claims

1. A variable tooth worm, characterized in that: The invention comprises a shaft body (1) and thread teeth (2) arranged on the shaft body (1); the lead of the thread teeth (2) remains unchanged along the entire length of the worm; the root surface of the thread teeth (2) is arranged as a cylindrical surface or a circular arc rotation surface; and the top surface of the thread teeth (2) is arranged as a cylindrical surface or a circular arc rotation surface.

2. The variable tooth worm according to claim 1, characterized in that: The thread teeth (2) are formed by sweeping a straight blade along a spatial constant lead variable diameter helix, wherein the lead of the spatial constant lead variable diameter helix remains constant and the diameter varies with the axial position.

3. The variable tooth worm according to claim 1, characterized in that: The mathematical equation of the spatial constant lead variable diameter helix is: z=z1 Where z1 is obtained by solving the equation: Where: P is the helical lead, r1 is the worm pitch circle radius, r2 is the worm wheel pitch circle radius, α is the worm thread tooth profile pressure angle, and θ is the helical parameter (independent variable).

4. The variable tooth worm according to claim 1, characterized in that: The tooth top surfaces at both ends of the threaded teeth (2) are set as cylindrical surfaces, and the middle tooth top surface is set as a circular arc rotation surface.

5. The variable tooth worm according to claim 1, characterized in that: The number of teeth located within the tooth top circular arc rotation surface of the threaded teeth (2) is 4-6.

6. The variable tooth worm according to claim 1, characterized in that: The arc radius of the tooth top circular arc rotation surface of the threaded tooth (2) is 1.04-1.11 times the radius of the tooth root circle of the matched worm gear.

7. The variable tooth worm according to claim 1, characterized in that: The base reference surface of the worm tooth surface is a cylindrical surface.

8. A method for processing a variable tooth worm according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Perform rough and fine machining on the worm blank to form an external dimension reference; S2. slotting the worm blank according to the spatial constant lead variable diameter helix; S3. Tempering or quenching the slotted worm; S4, trimming the toothed grinding wheel using a CNC machine tool to form an envelope surface, and grinding along the spiral line to form thread teeth; S5. Perform gear hobbing on the worm gear blank to form a finished worm gear.

9. The processing method according to claim 8, characterized in that: In step S4, the CNC machine tool uses five-axis linkage control to complete the trimming of the envelope surface and the grinding of the thread teeth.

10. The processing method according to claim 8, characterized in that: During the meshing process between the worm wheel and the worm, the tooth surface of the worm wheel and the thread teeth of the worm form four to five pairs of continuously meshing contact areas.

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