Precise enhanced cam roller worm gear

Abstract

A precision enhanced cam roller worm gear belongs to the field of machinery. The structure comprises a worm gear with a cam roller string, a worm and a structure body for connecting and supporting, a groove is machined in the circumference of the worm wheel disc, and the curvature center of the groove points to the axis of the worm. The rotation centers of the cam rollers in the cam roller string are located on at least two concentric lines, and the cam roller shafts in the cam roller string are connected through combined longitudinal beams. The problem of rotation interference when touching the left and right sides of the same cam roller; therefore, along with the rotation of the worm, different cam rollers are shifted to rotate and do not interfere with each other, so that the zero back clearance of the turbine worm system is not limited; and the method can be widely applied to the field with precise high-torque requirements.

Description

[Technical Field]

[0001] This invention belongs to the field of mechanical technology. More precisely, it is a rolling mechanism that uses multiple rows of non-concentric rolling cam rollers as worm gear contacts to improve the operational accuracy of existing technologies. [Background Technology]

[0002] Worm gears have been around for over 100 years and are commonly used to transmit motion and power between two intersecting shafts. In their mid-plane, the worm wheel and worm are equivalent to a gear and rack, and the worm itself is similar in shape to a screw.

[0003] The basic parameters of a conventional worm gear are: module m, pressure angle, worm diameter coefficient q, lead angle, number of worm threads, number of worm wheel teeth, addendum coefficient (taken as 1), and clearance coefficient (taken as 0.2). Among these, module m and pressure angle refer to the module and pressure angle of the worm shaft surface, i.e., the module and pressure angle of the worm wheel end face, and are both standard values; the worm diameter coefficient q is the ratio of the worm's pitch circle diameter to its module m. Operating characteristics: 1. It can achieve a large transmission ratio and is more compact than a crossed-axis helical gear mechanism. 2. The meshing tooth surfaces of the two wheels are in line contact, and its load-bearing capacity is much higher than that of a crossed-axis helical gear mechanism. 3. Worm drive is equivalent to helical drive, a multi-tooth meshing drive, so the transmission is smooth and the noise is very low. 4. It has self-locking property. When the lead angle of the worm is less than the equivalent friction angle between the meshing teeth, the mechanism has self-locking property, which can achieve reverse self-locking, that is, only the worm can drive the worm wheel, and the worm wheel cannot drive the worm. For example, the self-locking worm gear mechanism used in lifting machinery can provide safety protection through its reverse self-locking property. 5. Low transmission efficiency and severe wear. During worm gear meshing transmission, the relative sliding speed between the meshing teeth is high, resulting in high friction loss and low efficiency. On the other hand, the high relative sliding speed also leads to severe tooth surface wear and heat generation. To dissipate heat and reduce wear, relatively expensive materials with good friction-reducing and wear-resistant properties, as well as good lubrication devices, are often used, thus increasing costs. 6. The axial force of the worm is relatively large.

[0004] Improved Cam Roller Type: As early as the 1950s, due to the large transmission ratio and reverse self-locking of worm gears, which are the biggest advantages of this transmission method, it was frequently used in the B-axis of horizontal machining centers in precision machinery applications. It features a large speed ratio, good rigidity, and the ability to achieve zero backlash. The following are several methods for achieving zero backlash in worm gear drives: Adjusting the center distance: During the design phase, the backlash is minimized by adjusting the center distance dimensions. However, it is necessary to consider that manufacturing tolerances of the worm gear, housing center distance tolerances, and thermal deformation will all affect the final assembly. The backlash is significant, and the transmission pair cannot be readjusted after wear. A pre-tensioned worm gear eliminates backlash by using springs to pre-tension two worm gears, clamping the meshing worm teeth between the pre-tensioned worm gears. However, limited by spring stiffness, it can only be used in light-load applications. Another option is the OTT worm gear, commonly used in the machine tool industry. To achieve high rotational accuracy, this solution features multi-tooth meshing (high stiffness) and easy backlash adjustment. Compared to a double-lead worm gear, this solution is more suitable for the stiffness and accuracy requirements of the machine tool industry.

[0005] In recent years, the backlash has been adjusted by axial movement of a hollow worm sleeve. The cam rollers around the worm and worm wheel mesh with the tooth surface of the worm wheel during forward and reverse rotation, respectively, to achieve the requirement of zero backlash.

[0006] Overview of the advantages and disadvantages of traditional worm gears:

[0007] Compared with other forms of gear transmission, worm gear drives have the following advantages and disadvantages.

[0008] advantage:

[0009] *Large single-stage speed ratio: The maximum single-stage speed ratio of bevel gear drives and spur gear drives is generally around 1 / 10, while worm gear drives with speed ratios of 1 / 70-1 / 100 are easy to manufacture. Therefore, worm gear reducers can achieve large speed ratios with relatively small overall dimensions. The image shows a comparison between worm gear reducers and helical gear reducers with speed ratios of 1 / 5, 1 / 25, 1 / 70, and 1 / 150, each with a transmission power of 30 horsepower and an input shaft speed of 1200 rpm.

[0010] *Low operating noise and vibration: When reciprocating gears and bevel gears mesh, they mainly engage in rolling contact, while worm gears mainly engage in sliding contact. Therefore, there are fewer factors that generate noise and vibration. For this reason, worm gear reducers are preferred for driving escalators, elevators, moving walkways, and, in recent years, machines designed to prevent pollution.

[0011] *Use a worm gear reducer. The shafts can be arranged perpendicularly without intersecting each other: the arrangement of the worm shaft and worm wheel shaft can sometimes be both convenient and reasonable, saving installation space for the prime mover and driven mover.

[0012] *It can prevent reverse rotation: When the worm lead angle is less than the friction angle, theoretically, the worm gear cannot drive the worm, meaning a self-locking worm gear transmission device can be designed. However, in reality, the tooth surface friction coefficient changes from static friction coefficient to dynamic friction coefficient due to vibration and other reasons, so it may rotate slowly at times, making it difficult to achieve complete self-locking.

[0013] Disadvantages: Existing worm gear mechanisms all use a common high-friction tooth contact operation mode, which not only results in low transmission efficiency and tooth backlash, but also has a very limited contact area between the teeth.

[0014] *Low efficiency: Compared to other types of N-gear drives, worm gear drives suffer from high frictional losses during power transmission, resulting in low efficiency. Currently, due to improved manufacturing methods, near-theoretical efficiencies can be achieved; some worm gear drives reach 98% efficiency at a speed ratio of 1 / 5 and a worm speed of 180 rpm. However, with the same center distance, at a speed ratio of 1 / 70 and a worm speed of 200 rpm, the efficiency is approximately 60%.

[0015] *Prone to tooth surface adhesion: Involute cylindrical gears, when subjected to load, experience a positive change in tooth contact due to deformation of various parts. However, in worm gear drives, the tooth contact changes negatively, deforming towards the rupture of the oil film on the tooth surface, making tooth surface adhesion more likely. Therefore, the amount of deformation should be estimated and adjusted during assembly to ensure proper tooth contact and bearing clearance. Furthermore, careful running-in operation is essential.

[0016] *Lifespan and cost issues: Worm gear drives use copper alloy materials. Since dedicated gear cutting machines are generally unavailable, gear cutting efficiency is low, and manual tooth surface dressing is very time-consuming.

[0017] Advantages and disadvantages of cam roller worm gear:

[0018] Cam roller drives achieve zero backlash by radial preload and optimizing the dimensions of the rollers and worm gears. They also utilize rolling friction instead of sliding friction on the meshing surfaces, enabling high-efficiency, high-torque transmission in positioning systems. Furthermore, this transmission method features high rigidity and good accuracy retention, and is commonly used in the B-axis applications of horizontal machining centers.

[0019] This technology has achieved good results in many fields; however, due to limitations in the size, strength, and geometric transmission ripple of the cam rollers, there is still room for improvement in terms of transmission accuracy, service life, and other aspects. [Summary of the Invention]

[0020] The purpose of this invention:

[0021] To overcome the shortcomings of existing technologies and improve the operation of current worm gears with cam roller structures, such as the lack of precision in transmission matching and service life.

[0022] The features of this invention are: compact structure, high transmission accuracy, and long service life.

[0023] The key technology of this invention is to create geometric conditions that allow for full contact and no interference between the worm gear threads, and to cleverly utilize the concept of longitudinal bearing pressure, by refining the thread joint to achieve zero backlash, thus obtaining a more perfect structure.

[0024] Specific details of the invention:

[0025] The precision-enhanced cam roller worm gear consists of: a worm gear with cam roller strings, a worm, and connecting and supporting components; grooves are machined on the circumference of the worm gear disc, with the center of curvature of the grooves pointing towards the axis of the worm; 2-8 rows of cam rollers are installed within the grooves; each row of cam rollers is staggered, forming rows of oblique cam roller strings when viewed along the axial direction of the worm gear shaft, with each string containing 2-8 cam rollers (the same number as the rows); a connecting beam connects the individual cam rollers in the cam roller strings (through fitting holes, welding, bonding, etc.). (etc.) to form a mechanical whole, increasing its collective strength; however, if it is not necessary to increase the joint strength, the joint beam can be omitted, or a separate snap ring-like structure can be used to lock the cam rollers from jumping out, or cam roller shafts with end caps can be used to seal the individual cam rollers; even the two ends of the joint beam can be extended and bent to contact and root near the edge of the worm gear disk to further increase the strength without hindering the rotation of the worm; another construction is that the cam rollers and cam roller shafts are integrated, with the cam roller shafts inserted into the bearing holes on the circumference of the worm gear disk and able to rotate freely.

[0026] Looking from a position perpendicular to the worm gear shaft, the rotation centers of the cam roller shafts in the cam roller set are all located on at least two common tangents (the direction of the common tangent is the tangent direction of the worm helix; the angle between this direction and the worm axis, two skew lines, is between 0 and 90 degrees, with the angle being larger as the lead of the pitch decreases). Thus, when the two slopes of the worm's helical recess simultaneously contact the same cam roller set, they will touch both sides of the cam roller set; however, the slopes on both sides of the worm's helical recess will not touch the same cam roller. The left and right sides will not cause the same-direction movement of the two ramps constructed by the spiral recess of the worm, and the rotational interference problem when the left and right sides touch the same cam roller (which will prevent the cam rollers touched by the left and right sides at the same time from rotating); therefore, as the worm rotates, it will cause different cam rollers to rotate without interfering with each other, which makes the zero backlash of the worm gear system unrestricted (due to the unique structure, the arrangement of zero backlash between the worm wheel and the worm can be unrestricted, and all contact points can be designed with zero backlash).

[0027] It should be noted that the combination of three wheels in the cam roller set is the most advantageous. Choosing the middle cam roller to be slightly larger than the two outer cam rollers best conforms to the scientific principle of force distribution. In terms of geometric layout, the two curved surfaces of the worm gear helix correspond to the cam rollers at equal positions (axial direction), making it easy to mathematically determine zero backlash between the cam rollers and the worm gear helix. Moreover, the number of contact points is more than double that of existing Taiwanese technologies. Under the same torque requirements, the volume is reduced by at least 30%.

[0028] Furthermore: the circumferential groove may not exist, and instead 2-8 rows of cam rollers are directly installed on a cylindrical structure; the orientation of each row of cam rollers can be radial, vertical and away from the central axis, or each row can be a curved roller shaft that makes the corresponding cam roller point towards the central axis of the worm.

[0029] This invention brings about three major technological advancements:

[0030] Firstly, the discrete multi-cam roller string structure allows for a reduction in the diameter of individual cam rollers, resulting in a smaller worm pitch and more refined transmission potential. Secondly, the zero backlash in more parts facilitates the ability to withstand greater forces. Thirdly, it is conducive to miniaturization and improved lifespan. [Image Description]

[0031] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments:

[0032] [ Figure 1 ] Precision enhanced cam roller worm gear structure and exploded view.

[0033] [ Figure 2 Schematic diagram showing the positional relationship between the worm gear structure and the cam roller string.

[0034] [ Figure 3 A cross-sectional schematic diagram of worm gear meshing.

[0035] Explanation of the labels in the diagram:

[0036] 1 worm gear

[0037] 1-1 Circumferential Groove

[0038] 1-2 worm gear shaft

[0039] 1-3 worm gear

[0040] 1-4 roller shafts

[0041] 1-5 Cam Roller 1

[0042] 1-6 Cam Roller 2

[0043] 1-7 Cam Roller 3

[0044] 1-8 longitudinal beams

[0045] 1-9 Cam Roller Set

[0046] 2 worm gears

[0047] 3 Structures

[0048] 4 back gap

[0049] 5 tangent 1

[0050] 6 male tangent 2

[0051] 7. Reinforced end

[0052] 8. Connecting lines

[0053] 9. Local magnification

[0054] 10. Mid-section of the worm gear disk [Detailed Implementation]

[0055] like Figure 1 , Figure 2 As shown:

[0056] The worm wheel 1 and worm shaft 2 are supported by structure 3 and can rotate freely. Three rows of cam rollers are installed in the circumferential groove 1-1 of the worm wheel disk 1-3. Each row has three cam rollers: cam rollers 1, 1-5, cam rollers 2, 1-6, and cam rollers 3, 1-7. The longitudinal beam 1-8 connects the roller shafts 1-4 that constrain the above three cam rollers, making them a mechanical whole. All roller shafts 1-4 are inserted into the hole of the worm wheel disk and pass through the central hole of the cam roller to constrain its rotation. The reinforcing end 7 can be connected to the edge of the worm wheel disk 1-3 to further increase its overall strength. It should be noted that the combination of the three wheels in the cam roller series 1-9 is the most advantageous. Choosing the middle cam roller 2, 1-6 is slightly larger than the cam roller 1, 1-5 and the cam roller 3, 1-7, which is in line with the scientific principle of force distribution. Since the two sides of the worm helix correspond to the cam rollers at the same position (axial direction), it is easy to determine the zero backlash between the cam roller and the worm helix through mathematical deduction.

[0057] Each cam roller string 1-9 has 3 cam rollers. When viewed perpendicularly to the worm gear axis, looking at the end face of the worm gear disc, common tangents 1 and 5 are parallel to common tangents 2 and 6; as shown... Figure 2 As shown in the enlarged section 9, the cam roller strings 1-9 are connected together by the longitudinal beams 1-8. When a straight line is drawn through the three cam roller strings along the direction of the worm's spiral angle (the tangent of the spiral), there are common tangents 1 and 5 at the lower angle, while at the upper angle, due to the obstruction of the protruding cam rollers 2 and 1-6, the common tangents 2 and 6 are only tangent to the upper part of the cam rollers 2 and 1-6. The direction of the connecting line 8 is also the direction of the common tangent, and the centers of the three cam rollers are located between two different connecting lines. That is to say, when the two opposite slopes of the spiral concave structure of the worm 2 simultaneously contact the same cam roller string, they will touch the left and right sides of the cam roller string 1-9. As the worm 2 rotates, it actuates the different cam rollers (one side actuates cam rollers 1, 1-5 and cam rollers 3, 1-7, and the other side actuates cam rollers 2, 1-6), without interfering with each other.

[0058] Due to its unique structure, the zero-backlash arrangement between the worm gear and the worm can be unrestricted, with all contact points being zero-backlash. This brings three major advantages: First, the discrete multi-cam roller string structure facilitates the reduction of the diameter of individual cam rollers, resulting in a smaller worm pitch and more refined transmission potential; second, the zero-backlash design in more areas helps withstand greater forces; and third, it facilitates miniaturization and improves service life.

[0059] like Figure 3 As shown:

[0060] Structure 3 supports the rotation of the worm gear disk 1-3 and the worm 2. The cross section of this figure is perpendicular to the worm gear shaft and crosses the middle section 10 of the worm gear disk, where the cam rollers 2, 1-6, roller shaft 1-4 and longitudinal beam 1-8 can be clearly seen. The helix of the worm 2 can simultaneously touch the cam rollers 2, 1-6 and cam rollers 3, 1-7 with zero backlash 4. Due to the non-coincidence of the connecting lines, the same cam roller cannot simultaneously touch the side wall of the worm helix, thus not interfering with the rotation of the rollers.

Claims

1. A precision-enhanced cam roller worm gear, comprising the following components: A worm gear with cam roller strings, a worm, and a connecting and supporting structure; grooves are machined on the circumference of the worm gear disc, with the center of curvature of the grooves pointing towards the axis of the worm; and 2-8 rows of cam rollers are installed in the grooves; each row of cam rollers in the grooves is staggered, forming rows of oblique cam roller strings when viewed along the axial direction of the worm gear shaft, with 2-8 cam rollers in each string; Its characteristics are: Viewed from a position perpendicular to the worm gear shaft, the rotation centers of the cam rollers in the cam roller string are all located on at least two connecting lines. Thus, when the two ramps of the worm's helical recess simultaneously contact the same cam roller string, and would touch the left and right sides of that cam roller string, the ramps on both sides of the worm's helical recess will not touch the left and right sides of the same cam roller. This avoids the rotational interference problem caused by the unidirectional movement of the two ramps of the worm's helical recess touching the left and right sides of the same cam roller. Therefore, as the worm rotates, different cam rollers rotate without interference, making zero backlash in the worm gear system unrestricted. Using a connecting beam can connect the individual cam rollers in the cam roller train. The ends of the connecting beam can even be extended and bent to contact and anchor near the edge of the worm gear disc to further increase strength; or individual snap rings can be used to seal the individual cam rollers, or cam roller shafts with end caps can be used directly.

2. The precision-enhanced cam roller worm gear according to claim 1, characterized in that... The grooves machined on the circumference of the worm gear disc may not exist; instead, 2-8 rows of cam rollers are directly mounted on a cylindrical structure. The orientation of each row of cam rollers can be radial, perpendicular, and away from the central axis, or each row can be formed by curved roller shafts that make the corresponding cam rollers point towards the central axis of the worm.

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