An instantaneous high load capacity worm drive mechanism for valve actuators

Abstract

The utility model discloses a kind of instantaneous high bearing worm drive mechanisms for valve actuator, including when being opened or closed to valve, driving torque is transmitted to worm through input shaft, worm starts to rotate after special profile optimization, its division circle tooth thickness b1 is designed as 35% to 42% of pitch P;The utility model passes through with worm division circle tooth thickness b1 design as 35%~42% of pitch P, worm gear division circle tooth thickness b2 increases to 58%~65% of pitch P, and is combined with 14°~18° pressure angle α and 0.5~1.3 displacement coefficient x2, simultaneously meshing tooth number is greater than 2, significantly improve the root bending strength and instantaneous overload capacity, simultaneously, worm front end adopts the shaft sleeve of smaller outer diameter to bear radial force, tail part is provided with thrust ball bearing to bear axial force, substantially shorten the support span L, allow to reduce worm division circle diameter and increase helix angle, to drive efficiency is improved about 13%, material consumption reduces, the unity of high strength and high efficiency is realized.

Description

Technical Field

[0001] This utility model relates to the technical field of valve actuators or manual worm gear operators, specifically a high-load-bearing worm gear transmission mechanism for valve actuators. Background Technology

[0002] Valve drive devices (such as electric actuators and worm gear manipulators) commonly use Archimedes' cylindrical worm gear transmission. Due to the low frequency of valve switching, but the extremely high instantaneous load at the end of the switching process (up to 2-3 times the intermediate operating load), traditional designs have significant drawbacks: 1) To meet deflection requirements, the worm support span is large, the diameter is large, and the helix angle is small, resulting in low transmission efficiency and material waste; 2) Standard worm gear transmissions take tooth surface contact stress as the main design target, and the worm wheel tooth thickness is equal to the worm tooth thickness, failing to optimize for the difference in material strength between the two, resulting in easy breakage of the worm wheel tooth root; 3) Integrated worm gears require a large number of semi-finished products to adapt to different valve stems, resulting in high inventory costs; 4) Traditional sealing and support methods are not reliable enough in harsh environments, and the assembly process also limits structural optimization.

[0003] Therefore, there is an urgent need for a special worm gear transmission mechanism that has strong load-bearing capacity, high efficiency, compact structure, low cost, and is suitable for valve switching characteristics. Utility Model Content

[0004] The purpose of this invention is to provide an instantaneous high-load worm gear transmission mechanism for valve actuators, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: an instantaneous high-load-bearing worm gear transmission mechanism for valve actuators, comprising a valve body and a worm and a worm wheel inside it. Through tooth profile optimization, the number of teeth simultaneously meshing during transmission is greater than a certain value, wherein: the pitch circle tooth thickness b1 of the worm is 35% to 42% of the tooth pitch P, and the pitch circle tooth thickness b2 of the worm wheel is 58% to 65% of the tooth pitch P; the pressure angle α of the worm gear transmission mechanism is 14° to 18°, and the displacement coefficient x2 is 0.5 to 1.3.

[0006] Preferably, both ends of the worm are supported on the housing by bearings. The support component at the front end of the worm includes a bushing with an outer diameter smaller than that of a rolling bearing to bear radial force, and the tail end of the worm is provided with a thrust ball bearing to bear axial force, so as to shorten the support span L of the worm.

[0007] Preferably, the bushing is an iron-based or copper-based powder metallurgy bearing, a sintered oil-impregnated bearing, or a graphite-filled PTFE oil-free lubricated bearing.

[0008] Preferably, the lower part of the outer casing is provided with an integrally formed lower chamber, which is a closed or open structure, used to reduce the positioning height dimension H of the worm gear and avoid porosity defects during the casting of the outer casing.

[0009] Preferably, the worm gear is connected to a separate drive component via an involute spline.

[0010] Preferably, it also includes a windproof, sandproof, and rainproof sealing structure, including a sealing ring disposed between the upper part of the worm gear and the outer casing.

[0011] Preferably, the component includes an adjusting screw arranged in sequence, a filler filling the threaded hole of the housing, a filler sleeve fitted on the adjusting screw, and a nut for tightening the filler sleeve.

[0012] Preferably, the filler is a rubber, PTFE, flexible graphite, or carbon fiber material.

[0013] Preferably, the assembly includes the following steps: first, one end of the worm gear is initially installed into the housing; then, the worm is heated to a temperature lower than its material tempering temperature; then, with the assistance of a special fixture, the heated worm undergoes elastic deformation to create assembly space; then, the threads of the worm are screwed into the tooth groove of the worm gear; finally, after the worm has cooled, the assembly is completed.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] 1. This utility model effectively solves the problems of easy tooth root fracture and low transmission efficiency of traditional worm gear drives under instantaneous high load at the valve end by adopting an asymmetric tooth profile optimization design and a compact support structure. Specifically, the tooth thickness b1 of the worm pitch circle is designed to be 35% to 42% of the tooth pitch P, and the tooth thickness b2 of the worm wheel pitch circle is increased to 58% to 65% of the tooth pitch P. Combined with a pressure angle α of 14° to 18° and a displacement coefficient x2 of 0.5 to 1.3, the number of teeth meshing at the same time is greater than 2, which significantly improves the tooth root bending strength and instantaneous overload capacity. At the same time, a bushing with a smaller outer diameter is used at the front end of the worm to bear the radial force, and a thrust ball bearing is set at the tail end to bear the axial force. The support span L is greatly shortened, allowing for a reduction in the worm pitch circle diameter and an increase in the helix angle, thereby improving the transmission efficiency by about 13% and reducing the amount of material used, achieving a balance between high strength and high efficiency.

[0016] 2. This utility model significantly reduces manufacturing costs and inventory pressure through modular drive connection, integrated lower chamber structure and multiple sealing solutions, and improves reliability in harsh environments. The worm gear is connected to an independent drive component through an involute spline, which allows the worm gear to be mass-produced as a standard part. Only different specifications of drive components need to be stocked, realizing zero inventory management and greatly reducing capital occupation and supply chain complexity.

[0017] Meanwhile, the integrated closed or open lower chamber of the outer shell reduces the positioning height dimension H of the worm gear, avoids casting porosity defects, reduces weight, and reduces the amount of grease filling. In addition, the sealing ring on the upper part of the worm gear and the packing seal assembly at the adjusting screw together form a double barrier against wind, sand, rain and high-pressure media, achieving a protection level of up to IP68, ensuring long-term stable operation of the mechanism under various harsh working conditions such as open air, desert or deep sea. Attached Figure Description

[0018] Figure 1 A schematic diagram of the tooth thickness and pressure angle parameters of the worm gear transmission mechanism of the present invention;

[0019] Figure 2 A partial cross-sectional view of the worm gear support structure of the present invention;

[0020] Figure 3 A cross-sectional view of the overall structure of one embodiment of the present invention (with a closed lower chamber);

[0021] Figure 4 A schematic diagram of another embodiment of the present invention (with an open lower chamber);

[0022] Figure 5 A partial schematic diagram of the windproof, sandproof, and rainproof sealing structure of the present invention;

[0023] Figure 6 A partial cross-sectional view of the adjusting screw sealing structure of the present invention;

[0024] Figure 7 A cross-sectional view of the worm gear actuator body of the present invention.

[0025] Explanation of reference numerals in the attached diagram: 1-worm gear; 2-worm wheel; 3-housing; 4-shaft sleeve; 5-thrust ball bearing; 6-lower chamber; 7-drive component; 8-seal ring (O-ring); 9-adjusting screw; 10-packing; 11-packing sleeve; 12-nut. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] Example 1: Please refer to Figures 1-7This utility model provides a technical solution: an instantaneous high load-bearing worm gear transmission mechanism for valve actuators, including a valve body, a worm 1, a worm wheel 2, a housing 3, a bushing 4, a thrust ball bearing 5, a lower chamber 6, a drive component 7, a sealing ring 8, an adjusting screw 9, packing 10, a packing sleeve 11, and a nut 12.

[0028] Firstly, regarding the optimization of tooth profile parameters:

[0029] In this embodiment, the module m = 4 mm and the tooth pitch P = π·m ≈ 12.56 mm.

[0030] The worm gear 1 is made of 42CrMo alloy steel. After heat treatment, the tooth surface is high-frequency quenched to a hardness of HRC45-50. Its yield strength is far greater than that of the worm wheel material. The worm wheel 2 is cast from ZCuSn10P1 tin bronze. Based on the huge difference in the properties of the two materials, the tooth thickness is asymmetrically distributed: the tooth thickness b1 of the worm gear pitch circle is designed to be 4.7mm (about 37.4% of the tooth pitch P), and the tooth thickness b2 of the worm wheel pitch circle is designed to be 7.86mm (about 62.6% of the tooth pitch P).

[0031] The pressure angle α of the transmission is set to 16°, which is less than the standard 20° pressure angle, in order to increase the useful component force and improve the transmission efficiency. Through modeling and calculation, the displacement coefficient x2 is determined to be 0.8. This combination optimization enables the number of teeth meshing at the same time to reach 2.3, which significantly improves the tooth root bending strength and instantaneous overload capacity. After testing, its output torque and fatigue life are 1.7 times higher than the standard ZA worm gear transmission.

[0032] Secondly, the optimization of the support structure:

[0033] It should be noted that the worm 1 is mounted on the housing 3 via support structures at both ends. At the front end of the worm 1 (the end closest to the input shaft), a copper-based powder metallurgy bushing 4 is provided to bear the radial force. The outer diameter of this bushing 4 is 25mm, which is much smaller than that of a deep groove ball bearing under the same load, thus allowing for an increase in the wall thickness of the support hole and a more compact structure. At the tail end of the worm 1, a pair of thrust ball bearings 5 ​​(model 51204) mounted back to back are provided to bear the axial force. This support combination reduces the support span L of the worm from the traditional 120mm to 75mm. The reduction in span allows for a corresponding decrease in the pitch circle diameter d1 of the worm, thereby increasing the helix angle λ of the worm to 12°. According to calculations, these two improvements together increase the transmission efficiency by approximately 13%.

[0034] Thirdly, the optimization of the worm gear box and lower chamber structure:

[0035] The outer casing 3 is integrally cast from HT250 gray cast iron, with a closed lower chamber 6 at its bottom. The presence of this lower chamber 6 reduces the required positioning height H of the worm gear 2 from 45mm to 28mm, avoiding a large amount of redundant metal material below the worm gear, making the worm gear 2 structure lighter. More importantly, during the casting process, the upper and lower walls of the lower chamber 6 effectively compensate for the shrinkage of the connecting bolt joints, completely eliminating casting defects such as porosity and looseness that are easily caused by excessively high bolt joints in traditional structures, thus improving product yield. In addition, the lower chamber 6 also reduces the useless space in the upper cavity of the outer casing 3, reduces the amount of grease filling, and lowers costs.

[0036] The optimization of the fourth drive component connection:

[0037] By machining an internal spline at the center of the worm gear 2, it connects to an independent 45 steel heat-treated drive component 7 via an involute spline. The drive component 7 can be machined individually according to the specific dimensions of the customer's valve stem and keyway requirements. This design allows the worm gear 2 to be pre-machined as a standard part, achieving zero inventory management. Only drive components 7 of different specifications need to be stocked, greatly reducing inventory costs and capital occupation. During installation, the drive component 7 can be installed on the valve stem first, and then the entire transmission mechanism can be fitted in. The position of the switch indicator plate can be adjusted by rotating it several small angles, making installation convenient.

[0038] Fifth, optimization of the sealing structure:

[0039] Sand and rainproof seal: A nitrile rubber sealing ring 8 is installed at the fit gap between the upper part of the worm gear 2 and the housing 3 to effectively prevent sand and rain from entering the interior of the mechanism from the top, ensuring the reliability of long-term operation in open-air or desert environments. At the same time, high-pressure sealing is achieved by adjusting the screw: The adjusting screw 9 used to adjust the axial clearance of the worm gear adopts a unique sealing component. Flexible graphite filler 10 is filled into the threaded hole of the housing 3, then the filler sleeve 11 is put on, and finally the nut 12 is tightened to achieve a seal by compressing the filler 10. This structure is simple and reliable and can achieve an IP68 protection level. It is suitable for high-pressure and corrosive media conditions such as deep-sea valves. The filler material can be replaced with PTFE, carbon fiber, etc., depending on the working conditions, making it highly adaptable.

[0040] Sixth, optimization of assembly and manufacturing processes:

[0041] a. First, insert one end of the worm gear 2 into the predetermined position of the outer casing 3;

[0042] b. Place the worm gear 1 assembly with the bushing 4 and thrust ball bearing 5 installed into an oven, heat it to 180℃ (below its tempering temperature), and keep it at that temperature for a period of time;

[0043] c. Use a special fixture (not shown in the figure) to slightly pry open the tail of the worm 1, which has undergone elastic deformation after being heated, so as to make room for assembly.

[0044] d. Screw the thread of the worm 1 radially into the tooth groove of the pre-positioned worm wheel 2;

[0045] e. Remove the clamps and allow the worm gear 1 to cool to room temperature. Once its elastic deformation is restored, it will form a stable mesh with the worm wheel 2. Finally, install the bearing cover and other components.

[0046] Example 2: See Figure 4 The difference between this embodiment and Embodiment 1 is that:

[0047] The lower chamber 6 provided at the bottom of the outer casing 3 is an open lower chamber. This structure is suitable for products with top-mounted worm gear actuators (i.e., valve stems are installed from above). The open lower chamber 6 also has the beneficial effects of reducing weight, optimizing casting process, and reducing lubricant usage. The other structures in this embodiment are the same as in embodiment 1.

[0048] The instantaneous high-load worm gear transmission mechanism for valve actuators described in this utility model operates as follows: When the valve needs to be opened or closed, the driving torque is transmitted to the worm 1 through the input shaft. The worm 1, with its specially optimized tooth profile, begins to rotate. Its pitch circle tooth thickness b1 is designed to be 35% to 42% of the tooth pitch P, meshing with the worm wheel 2, whose pitch circle tooth thickness b2 is designed to be 58% to 65% of the tooth pitch P. The combined action of a pressure angle α of 14° to 18° and a displacement coefficient x2 of 0.5 to 1.3 further enhances its performance. In the transmission, the number of teeth meshing simultaneously is greater than 2, thereby amplifying the input torque and smoothly transmitting it to the worm wheel 2. During this process, the radial force at the front end of the worm 1 is borne by the bushing 4 with a smaller outer diameter, while the huge axial thrust generated at the tail end is borne by the thrust ball bearing 5. This compact support combination significantly shortens the support span L of the worm, ensuring high rigidity and stability of the transmission. The worm wheel 2 transmits the torque to an independent drive component 7 through its internal involute spline. The drive component 7 then directly drives the valve stem to rotate, realizing the precise opening and closing of the valve.

[0049] Secondly, to cope with harsh environments, the sealing ring 8 set between the upper part of the worm gear 2 and the outer shell 3 effectively prevents the intrusion of wind, sand and rainwater. At the same time, a high-pressure sealing component is provided at the adjusting screw 9 used to adjust the axial clearance of the worm gear: the filler 10 filled in the threaded hole of the outer shell is pressed by the filler sleeve 11 and the nut 12 to form a reliable static seal. The entire transmission mechanism is housed in the integrally cast outer shell 3. The integrated lower chamber 6 structure at its lower part not only reduces the positioning height dimension H of the worm gear 2 and avoids casting defects, but also reduces the internal cavity and the amount of grease used, making the structure more compact and efficient.

[0050] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0051] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-load-bearing instantaneous worm gear transmission mechanism for a valve actuator, comprising a valve body and a worm (1) and a worm wheel (2) inside therein, characterized in that: By optimizing the tooth profile, the number of teeth engaged simultaneously during transmission is greater than 2, wherein: the pitch circle tooth thickness b1 of the worm (1) is 35% to 42% of the tooth pitch P, the pitch circle tooth thickness b2 of the worm wheel (2) is 58% to 65% of the tooth pitch P; the pressure angle α of the worm transmission mechanism is 14° to 18°, and the displacement coefficient x2 is 0.5 to 1.

3.

2. The worm gear transmission mechanism according to claim 1, characterized in that: The two ends of the worm (1) are supported on the housing (3) by bearings. The support component at the front end of the worm includes a bushing (4) with an outer diameter smaller than that of a rolling bearing to bear radial force. The tail end of the worm (1) is provided with a thrust ball bearing (5) to bear axial force, so as to shorten the support span L of the worm (1).

3. The worm gear transmission mechanism according to claim 2, characterized in that: The bushing (4) is an iron-based or copper-based powder metallurgy bearing, a sintered oil-impregnated bearing, or a graphite-filled PTFE oil-free lubricated bearing.

4. The worm gear transmission mechanism according to claim 3, characterized in that: The lower part of the outer shell (3) is provided with an integrally formed lower chamber (6). The lower chamber is a closed or open structure, which is used to reduce the positioning height dimension H of the worm gear (2) and avoid porosity defects during the casting of the outer shell (3).

5. The worm gear transmission mechanism according to claim 1 or 4, characterized in that: The worm gear (2) is connected to an independent drive unit (7) via an involute spline.

6. The worm gear transmission mechanism according to claim 1, characterized in that: It also includes a windproof, sandproof and rainproof sealing structure, including a sealing ring (8) set between the upper part of the worm gear (2) and the outer shell (3).

7. The worm gear transmission mechanism according to claim 1, characterized in that: It also includes an adjusting screw sealing assembly, which includes an adjusting screw (9) arranged in sequence, a filler (10) filling the threaded hole of the housing, a filler sleeve (11) sleeved on the adjusting screw, and a nut (12) for tightening the filler sleeve.

8. The worm gear transmission mechanism according to claim 7, characterized in that: The filler (10) is made of rubber, PTFE, flexible graphite or carbon fiber.

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