Variable tooth worm gear and method of machining the same

Abstract

The application relates to a variable-tooth worm and a processing method thereof, and relates to the technical field of worm structure, which comprises a variable-tooth worm composed of a shaft body and a thread tooth arranged on the shaft body, the lead of the thread tooth is constant along the overall length of the worm, the tooth root surface and the tooth top surface can be cylindrical surfaces or circular arc rotary surfaces, the thread tooth is formed by sweeping a linear blade along a space constant-lead variable-diameter helix, a mathematical equation of the helix is given, the related structural parameters of the thread tooth are specifically limited, the processing method of the variable-tooth worm is introduced, and the steps of rough and fine machining of a blank, slotting, heat treatment, gear grinding and the like are included, a five-axis linkage control is adopted for a numerical control machine tool, and the meshing of the worm wheel and the worm can form four to five pairs of continuously meshed contact areas. The application achieves the technical effects of optimizing the structural design of the variable-tooth worm, improving the machining precision and quality, and improving the meshing performance of the worm wheel and the worm.

Description

Technical Field

[0001] This application relates to the field of worm gear technology, and in particular to a variable tooth worm gear and its processing method. Background Technology

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

[0003] The conventional cylindrical worm gear drive features a compact structure, small size, and low weight, which effectively saves installation space, making it particularly suitable for space-constrained mechanical systems. Furthermore, this transmission method is characterized by smooth transmission and low noise. This is because the meshing of the worm helical teeth and worm wheel teeth is a continuous line contact, without the abrupt tooth engagement and disengagement processes found in gear drives, thus significantly reducing vibration and noise. This makes it especially suitable for environments sensitive to noise and vibration.

[0004] Another noteworthy characteristic is the self-locking property of ordinary cylindrical worm gear drives. When the helix angle of the worm is very small, only the worm can drive the worm wheel to rotate, and the worm wheel cannot drive the worm to rotate in the opposite direction. This characteristic is particularly important in mechanical devices that require protection against reverse rotation, such as cranes and jacks.

[0005] However, conventional cylindrical worm gear drives also have some significant drawbacks. The most prominent problem is their low efficiency. This is mainly because the relatively high sliding speed exists during the meshing process of the worm and worm wheel, resulting in large frictional losses and thus affecting the overall transmission efficiency.

[0006] To address the low efficiency of conventional cylindrical worm gear drives, the industry developed the annular envelope worm gear. This type of worm gear has concave circular arcs as both its tooth tip and base circle, and a large number of meshing teeth, thus exhibiting high load-bearing capacity and transmission efficiency. However, the annular envelope worm gear also presents new challenges: high heat value, sensitivity to center distance and axial position, and difficulties in manufacturing and inspection, all contributing to its high manufacturing cost.

[0007] US Patent 6176148B1 discloses an improved design: a variable-tooth worm gear. The tip surface of this worm is cylindrical or convex, and the reference circle of the tooth surface is formed by rotating a curve, exhibiting variable tooth thickness and variable tooth height. This design improves load-bearing capacity and transmission efficiency during meshing, bringing transmission performance closer to ideal. Compared to cylindrical worm gears, it has a greater number of simultaneously meshing teeth, and the gears can gradually engage and disengage. Furthermore, it offers advantages such as lower oil churning losses, less stringent center distance requirements, and adjustable axial position.

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

[0009] To address the problem that existing worm gears still have insufficient load-bearing capacity under heavy-load conditions and cannot meet the needs of certain high-load applications, this application provides a variable-tooth worm gear and its processing method.

[0010] The variable tooth worm gear provided in this application adopts the following technical solution: A variable tooth worm gear includes a shaft and threaded teeth disposed on the shaft. The lead of the threaded teeth remains unchanged along the overall length of the worm gear. The root surface of the threaded teeth is set as a cylindrical surface or a circular arc surface. The top surface of the threaded teeth is set as a cylindrical surface or a circular arc surface.

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

[0012] Optionally, the thread teeth are formed by a straight cutting edge sweeping along a spatial constant lead variable diameter spiral, wherein the lead of the spatial constant lead variable diameter spiral remains constant and the diameter varies with the axial position.

[0013] By adopting the above technical solution, the thread teeth are swept by a straight cutting edge along a spatial constant lead variable diameter helix, and the lead of the helix is ​​constant while the diameter changes with the axial position. This ensures the constant lead 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 for the spatial constant-lead variable-diameter helix is:

[0015]

[0016] z = z1

[0017] Where z1 is obtained by solving the equation:

[0018]

[0019] In the formula: P is the helical lead, r1 is the pitch circle radius of the worm, r2 is the pitch circle radius of the worm wheel, α is the pressure angle of the worm screw teeth, and θ is the helical parameter (independent variable).

[0020] By adopting the above technical solution, the spatial constant lead variable diameter helix equation of the thread tooth is determined, which can ensure the constant lead variable diameter characteristic of the thread tooth in space, guarantee the accuracy of the tooth profile, and thus improve the load-bearing capacity of the variable tooth worm.

[0021] Optionally, the top surfaces of the threaded teeth at both ends are set as cylindrical surfaces, and the top surface of the middle tooth is set as an arc-shaped rotating surface.

[0022] By adopting the above technical solution, the thread lead of the variable tooth worm remains unchanged along the overall length. The root surface and the top surface of the tooth are cylindrical or circular arc surfaces. Setting the top surfaces of the two ends as cylindrical surfaces and the middle as circular arc surfaces can increase the load-bearing capacity of the worm. Maintaining a shape similar to a toroidal worm can improve the load-bearing capacity. At the same time, flattening the top parts of the teeth at both ends can increase the heat dissipation space and facilitate the formation of an oil film, thereby solving the problem of high heat value and also helping to reduce production costs.

[0023] Optionally, the number of teeth located within the arcuate rotational surface at the tip of the thread tooth is 4-6.

[0024] By adopting the above technical solution, it can be ensured that a sufficient number of teeth participate in meshing simultaneously during the meshing process, so as to improve the stability and efficiency of the transmission. 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. At the same time, because an appropriate number of teeth are located in the tooth tip arc rotation surface, the high heat value problem caused by too many teeth is avoided. It also has a larger heat dissipation space to facilitate the formation of an oil film, and it is also conducive to controlling the accuracy during processing. With the help of CNC machine tools, the processing of this structure can be better realized.

[0025] Optionally, the radius of the arc of the tip of the threaded tooth is 1.04-1.11 times the radius of the root circle of the mating worm gear tooth.

[0026] By adopting the above technical solutions, the worm gear's basic transmission function can be guaranteed by setting threaded teeth on the shaft body with the threaded tooth lead remaining constant along the overall length of the worm, and setting the tooth root surface and tooth tip surface as cylindrical or circular arc surfaces. Setting the arc radius of the threaded tooth tip circular arc surface to 1.04-1.11 times the radius of the worm wheel tooth root circle 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.

[0027] Optionally, the reference surface of the worm gear tooth surface is a cylindrical surface.

[0028] By adopting the above technical solution, the reference surface being a cylindrical surface is beneficial for accurately determining the position and direction of the worm during manufacturing and assembly, improving machining accuracy, enabling the variable tooth worm to better cooperate with the worm wheel, reducing friction loss, and improving transmission efficiency.

[0029] A method for machining a variable-tooth worm gear, characterized by comprising the following steps:

[0030] S1. Rough and finish machining of the worm gear blank to form the external dimension reference;

[0031] S2. Grooving is performed on the worm gear blank according to the spatial constant lead variable diameter spiral.

[0032] S3. The worm gear after slotting is subjected to heat treatment or quenching.

[0033] S4. The toothed grinding wheel is dressed by a CNC machine tool to form an envelope surface, and the threaded teeth are formed by grinding along the spiral line.

[0034] S5. The worm gear blank is subjected to gear hobbing to form the finished worm gear.

[0035] 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.

[0036] Optionally, during the meshing process of the worm gear and the worm, the tooth surface of the worm gear and the threaded teeth of the worm form four to five pairs of continuously meshing contact areas.

[0037] In summary, this application includes at least one of the following beneficial technical effects:

[0038] 1. This application improves the load-bearing capacity of worm gear drives by adopting a variable tooth height design and a specific helical equation;

[0039] 2. This application simplifies the manufacturing method of the worm gear, thereby reducing manufacturing difficulty and cost;

[0040] 3. This application improves transmission efficiency by optimizing tooth profile design and meshing method, and has the advantages of increasing load-bearing capacity, reducing manufacturing difficulty and cost, and improving transmission efficiency. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the overall structure of a variable-tooth worm gear according to an embodiment of this application.

[0042] Figure 2 This is a schematic diagram illustrating the relationship between the tool installation and cutting motion in worm gear turning, as shown in the embodiments of this application.

[0043] Explanation of reference numerals in the attached diagram: 1. Shaft; 2. Thread teeth. Detailed Implementation

[0044] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification.

[0045] Please see Figure 1-2 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of this application and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of this application, should still fall within the scope of the technical content disclosed in this application. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of this application. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this application's implementation.

[0046] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0047] Example 1

[0048] This embodiment discloses a variable-tooth worm gear.

[0049] Reference Figure 1 The variable tooth worm gear provided in this application includes a shaft and threaded teeth disposed on the shaft. The shaft serves as the mounting base for the threaded teeth and provides support for them. The two are closely combined to form the variable tooth worm gear. This structure enables the variable tooth worm gear to perform stable transmission work, thereby improving the stability of the entire transmission system.

[0050] Specifically, shafts are generally made of metal, such as carbon steel or alloy steel, because they have good strength and toughness. Shafts are usually cylindrical, and their surfaces must have a certain degree of smoothness to reduce friction with other parts. Shafts can also be designed into other shapes according to actual needs, such as tapered shapes, to adapt to specific installation environments. When manufacturing shafts, the approximate shape can be obtained first by forging or rolling, and then the required precision can be achieved through machining processes such as turning and grinding.

[0051] The thread teeth are formed by a straight cutting edge sweeping along a spatial constant-lead variable-diameter helix. The mathematical equation for the spatial constant-lead variable-diameter helix is:

[0052]

[0053] Where z1 is obtained by solving the equation:

[0054]

[0055] In the formula: P is the helical lead, r1 is the pitch circle radius of the worm, r2 is the pitch circle radius of the worm wheel, α is the pressure angle of the worm screw teeth, and θ is the helical parameter (independent variable);

[0056] Here, the lead of the constant-lead variable-diameter spiral remains constant while the diameter varies with the axial position; this means that the lead of the thread teeth remains unchanged along the entire length of the worm, but the diameter will change; this special shape design can optimize 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, and the tip surface is set as a cylindrical surface or a circular arc surface.

[0057] For the tooth root surface, a cylindrical surface is relatively simple to manufacture and is suitable for applications where high precision is not required. However, a circular arc surface can better distribute stress and improve the strength of the tooth root. For example, in heavy-duty transmissions, a circular arc surface at the tooth root can effectively reduce the risk of tooth root fracture. The tooth tip surface is also designed as either a cylindrical or circular arc surface for similar reasons; a cylindrical tooth tip surface is easier to machine, while a circular arc surface allows for better engagement with the worm gear, improving transmission smoothness.

[0058] The top surfaces of the threaded teeth at both ends are cylindrical, while the top surface of the middle tooth is an arc-shaped rotating surface. This design allows the threaded teeth to play different roles in different parts. The cylindrical tooth top surfaces at both ends facilitate installation and positioning, while the arc-shaped rotating surface in the middle enhances the meshing effect with the worm gear and improves transmission efficiency. The number of teeth located in the arc-shaped rotating surface at the top of the threaded teeth is 4-6. This range of tooth count has been verified through extensive practical experience, ensuring load-bearing capacity without making the structure overly complex.

[0059] The radius of the arc of the tip circle of the thread tooth is 1.04-1.11 times the radius of the root circle of the mating worm gear tooth. This ratio ensures a good meshing clearance between the thread tooth and the worm gear, guaranteeing sufficient lubrication space and preventing transmission instability caused by excessive clearance. The reference surface of the worm tooth surface is a cylindrical surface, which helps to determine the accurate position and size during machining and inspection, improving production accuracy and quality.

[0060] The implementation principle of this embodiment is as follows: The variable-tooth worm gear of this embodiment optimizes the geometric parameters of the worm gear through a unique threaded tooth structure design, effectively improving its load-bearing capacity. The spatial constant lead variable diameter characteristic of the threaded teeth makes the force distribution more uniform during transmission, reducing the problem of local stress concentration. The reasonable setting of the tooth root surface and tooth tip surface ensures sufficient strength while improving the smoothness and efficiency of transmission. The different shapes of the tooth tip surfaces at both ends and in the middle, as well as the appropriate number of teeth and the ratio of the radius of the tooth tip arc to the radius of the worm wheel tooth root circle, further enhance the meshing effect between the worm and the worm wheel. Compared with the ordinary cylindrical worm gear and the annular envelope worm gear in the prior art, it has significant advantages in terms of load-bearing capacity, transmission efficiency, and cost, solving many problems existing in the prior art.

[0061] Example 2

[0062] The difference between this embodiment and the previous embodiment lies in the manufacturing process of the thread teeth. The thread teeth can be initially formed by casting, followed by minor machining adjustments. The casting material can be an alloy with good wear resistance, such as copper or aluminum alloys. Using casting can reduce production costs, making it particularly suitable for large-scale production.

[0063] The implementation principle of this embodiment is as follows: By changing the manufacturing process of the threaded teeth, this embodiment reduces production costs while ensuring the performance of the variable-tooth worm gear. The casting process can form relatively complex threaded tooth shapes in one step, reducing processing steps and time, and improving production efficiency. The selection of alloy materials with good wear resistance ensures the stable performance of the threaded teeth during long-term use, extending the service life of the variable-tooth worm gear. Compared with traditional processing methods, this embodiment achieves a better balance between cost and performance, further improving existing technology.

[0064] Example 3

[0065] The method for machining a variable-tooth worm gear provided in this application includes the following steps:

[0066] S1. Rough and finish machining of the worm gear blank to establish the external dimensional reference. First, select a suitable metal material as the worm gear blank, generally carbon steel or alloy steel. Then, use machine tools such as lathes and milling machines to rough machine the blank, removing most of the excess material and forming a rough shape. Next, finish machining is performed, using processes such as grinding, to bring the external dimensions of the worm gear to the required accuracy, providing an accurate reference for subsequent machining.

[0067] S2. Grooving is performed on the worm gear blank according to the spatial constant lead variable diameter helix. This step requires specialized grooving equipment, refer to... Figure 2 Based on the pre-set parameters of the spatial constant lead variable diameter helix, thread grooves are precisely cut into the worm gear blank. During the grooving process, it is essential to ensure that the movement trajectory of the tool strictly conforms to the requirements of the helix to guarantee the shape and dimensional accuracy of the thread teeth.

[0068] S3. The worm gear after slotting is subjected to quenching or tempering. Quenching and tempering can improve the overall mechanical properties of the worm gear, giving it both high strength and good toughness. Quenching can significantly improve the hardness and wear resistance of the worm gear. The specific treatment method used depends on the application and performance requirements of the worm gear.

[0069] S4. The toothed grinding wheel is dressed using a CNC machine tool to form an envelope surface, and then the thread teeth are formed by grinding along the helical line. The CNC machine tool can precisely control the motion trajectory and dressing parameters of the toothed grinding wheel to form an envelope surface that meets the requirements. Then, the grinding wheel grinds the worm gear along a spatial constant lead variable diameter helical line, ultimately forming precise thread teeth. In this process, the CNC machine tool uses five-axis linkage control to complete the dressing of the envelope surface and the grinding of the thread teeth. Five-axis linkage can achieve more complex movements, improving the accuracy and efficiency of machining.

[0070] S5. The worm gear blank is machined by gear hobbing to form the finished worm gear. A gear hobbing machine is used to machine the worm gear blank. Through the relative movement of the hob and the worm gear blank, the tooth profile of the worm gear is gradually cut out. During the machining process, it is essential to ensure that the parameters of the hob match the parameters of the worm to ensure good meshing between the worm gear and the worm.

[0071] The implementation principle of this embodiment is as follows: The processing method of this embodiment, through a series of rigorous steps, can accurately manufacture variable-tooth worm gears and worm wheels that meet design requirements. From rough and finish machining of the blank to grooving, heat treatment, and finally grinding and gear hobbing, each step is closely coordinated to ensure the precision and quality of the product. In particular, the five-axis linkage control of the CNC machine tool makes the machining more flexible and precise, enabling the machining of complex spatial constant lead variable-diameter helices. Compared with traditional machining processes, this entire processing method can better guarantee the performance of variable-tooth worm gears, improve production efficiency, reduce production costs, and effectively solve the problems of difficult machining and high costs in existing technologies.

[0072] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

[0073] The implementation principle of a variable tooth worm gear in this embodiment is as follows:

[0074] In summary, this application improves the load-bearing capacity of worm gear drives by employing a variable tooth height design and a specific helical equation; it reduces manufacturing difficulty and cost by simplifying the worm gear manufacturing method; and it enhances transmission efficiency by optimizing the tooth profile design and meshing method. Therefore, this application effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0075] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered within the protection scope of this application.

Claims

1. A variable-tooth worm gear, characterized in that, It includes a shaft (1) and threaded teeth (2) disposed on the shaft (1). The lead of the threaded teeth (2) remains constant along the overall length of the worm. The root surface of the threaded teeth (2) is set as a cylindrical surface or a circular arc surface. The top surface of the threaded teeth (2) is set as a cylindrical surface or a circular arc surface. The threaded teeth (2) are formed by sweeping a straight cutting edge along a spatial constant lead variable diameter spiral line. The lead of the spatial constant lead variable diameter spiral line remains constant and the diameter changes with the axial position. The mathematical equation for the spatial constant-lead variable-diameter spiral is: in, It is obtained by solving the equation: In the formula: P is the lead of the helix. Let be the pitch circle radius of the worm gear. Let α be the pitch circle radius of the worm gear, α be the pressure angle of the worm screw teeth, and θ be the helix parameter.

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

3. A variable tooth worm gear according to claim 1, characterized in that: The number of teeth located in the arc-shaped rotating surface at the tip of the thread tooth (2) is 4-6.

4. A variable tooth worm gear according to claim 1, characterized in that: The radius of the arc of the tip of the threaded tooth (2) is 1.04-1.11 times the radius of the root circle of the mating worm gear tooth.

5. A variable tooth worm gear according to claim 1, characterized in that: The reference surface for the worm gear tooth surface is a cylindrical surface.

6. A method for machining a variable-tooth worm gear as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Rough and finish machining of the worm gear blank to form the external dimension reference; S2. Grooving is performed on the worm gear blank according to the spatial constant lead variable diameter spiral. S3. The worm gear after slotting is subjected to heat treatment or quenching. S4. The toothed grinding wheel is dressed by a CNC machine tool to form an envelope surface, and the threaded teeth are formed by grinding along the spiral line. S5. The worm gear blank is subjected to gear hobbing to form the finished worm gear.

7. The processing method according to claim 6, characterized in that, In step S4, the CNC machine tool uses five-axis linkage control to complete the trimming of the envelope mother surface and the grinding of the thread teeth.

8. The processing method according to claim 6, characterized in that, During the meshing process of the worm gear and the worm, the tooth surface of the worm gear and the threaded teeth of the worm form four to five pairs of continuously meshing contact areas.

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