Zero-back-clearance flexible worm type worm and gear speed reducer

Abstract

The invention discloses a zero-back-clearance flexible worm type worm and gear speed reducer, and belongs to the field of machinery. The speed reducer comprises three parts, namely a flexible worm, a worm gear, a shell and a supporting part, according to the assembly relation, the shell and the supporting component are used for fixedly installing the flexible worm and the worm gear; the worm gear axis of the worm gear and the worm end shaft of the flexible worm are in a vertical driving relationship; when the bent flexible worm is bent and wraps the worm gear, a large number of teeth of the flexible worm make contact with the worm gear, and the flexible worm is of a long and thin spiral structure with the length-diameter ratio larger than 5. An end bearing serving as a supporting part keeps the tangential orientation of the circumference of a worm gear of an end shaft of the flexible worm, and meanwhile, under the supporting of the worm gear, the axis of the flexible worm is bent into an arc shape; the power rotating table can be widely applied to machine tools.

Description

[Technical field]

[0001] The present invention belongs to the field of mechanical technology, and is specifically a device that uses a bendable flexible worm as a component to drive a worm wheel, so as to improve the running accuracy of a reducer and increase rigidity. [Background Technology]

[0002] The worm gear structure is often used to transmit motion and power between two staggered axes. The worm wheel and worm are equivalent to the gear and rack in their middle plane, and the worm is similar in shape to the screw.

[0003] Basic parameters: module m, pressure angle, worm diameter coefficient q, lead angle, number of worm heads, number of worm wheel teeth, tooth top height coefficient (take 1) and top clearance coefficient (take 0.2). Among them, module m and pressure angle refer to the module and pressure angle of the worm shaft surface, that is, the module and pressure angle of the worm wheel end surface, and they are all standard values; worm diameter coefficient q is the ratio of the worm pitch circle diameter to its module m.

[0004] Operation characteristics: A large transmission ratio can be obtained, which is more compact than the staggered 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 the staggered helical gear mechanism. 3. The worm drive is equivalent to a spiral drive, which is a multi-tooth meshing drive, so the transmission is smooth and the noise is very low. 4. It has self-locking properties. When the lead angle of the worm is smaller than the equivalent friction angle between the meshing gear teeth, the mechanism has self-locking properties and 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 mechanism used in lifting machinery can play a safety protection role in its reverse self-locking property. 5. The transmission efficiency is low and the wear is severe. Worm gear meshing

[0005] During transmission, the relative sliding speed between meshing gear teeth is high, so the friction loss is large and the efficiency is low. On the other hand, the axial force of the worm is large, and the high relative sliding speed causes serious wear and heat generation on the tooth surface. In order to dissipate heat and reduce wear, more expensive materials with good anti-friction and wear resistance and good lubrication devices are often used, which results in high costs.

[0006] Pros and Cons Overview:

[0007] Compared with other forms of gear transmission, worm gear transmission (including machine tool turntable) has the following advantages and disadvantages.

[0008] advantage:

[0009] *Single-stage speed ratio is large:

[0010] The single-stage speed ratio of circular gear transmission and bevel gear transmission is generally about 1 / 10 at most, while the worm gear transmission with a speed ratio of 1 / 70-1 / 100 is easy to make. Therefore, the worm gear reducer can achieve a large speed ratio with a smaller size. It is often a comparison between the worm gear reducer with a speed ratio of 1 / 5, 1 / 25, 1 / 70, 1 / 150 and the helical gear reducer. Their transmission power is 30 horsepower and the input shaft speed is 1200 rpm.

[0011] * Low noise and vibration during operation: When the circular gear and the bevel gear are engaged, they are mainly in rolling contact, while the worm gear is mainly in sliding contact, so there are fewer factors that generate noise and vibration. For this reason, escalators, elevators, moving sidewalks, and pollution prevention machines in recent years all prefer to use worm gear reducers.

[0012] * Use worm gear reducer. The shafts can be arranged vertically without intersecting each other: the arrangement of the worm shaft and the worm wheel shaft can sometimes save the installation area of ​​the prime mover and the driven machine while being convenient and reasonable.

[0013] * Can prevent reversal: When the worm lead angle is smaller than the friction angle, the worm wheel cannot drive the worm in theory, which means that a self-locking worm transmission device can be designed. However, in reality, the friction coefficient of the tooth surface changes from static friction coefficient to dynamic friction coefficient due to vibration and other reasons, so it sometimes rotates slowly, and it is difficult to achieve complete self-locking.

[0014] Disadvantages: Existing worm gear mechanisms all use a common high-friction tooth contact operation mode. In addition to low transmission efficiency and tooth gap, the contact area of ​​the contact line between teeth is also very limited.

[0015] *Low efficiency: Compared with other forms of N-wheel transmission, worm gear transmission has large tooth surface friction loss and low efficiency when transmitting power. At present, due to the improvement of manufacturing methods, it can achieve an efficiency close to the theoretical value. Some worm gear transmissions have an efficiency of 98% when the speed ratio is 1 / 5 and the worm speed is 180 rpm. However, with the same center distance, if the speed ratio is 1 / 70 and the worm speed is 200 rpm, the efficiency is about 60%.

[0016] * Tooth surface adhesion is easy to occur: For cylindrical gears with involute tooth profile, if the tooth surface is under load, the gear tooth contact state changes to a better state due to the deformation of each part, while the gear tooth contact state of worm gear transmission changes to a worse state, that is, the gear surface oil film is deformed in the direction of rupture, which is easy to cause tooth surface adhesion. Therefore, the gear tooth contact state and bearing clearance during assembly should be adjusted according to the deformation amount. It is also necessary to perform the running-in operation as carefully as possible.

[0017] *Lifespan and cost issues: Worm gear transmission uses copper alloy materials. Since there are generally no special gear cutting machines, the gear cutting efficiency is low, and manual tooth surface finishing is very time-consuming. At the same time, low life also means poor accuracy retention, which not only makes it difficult to maintain machining accuracy, but also requires frequent maintenance. [Summary of the invention]

[0018] Purpose of the present invention:

[0019] The shortcomings of the existing technology are overcome, the contact area and transmission stiffness between the worm wheel and the worm are improved, and the accuracy retention and service life are extended.

[0020] Features of the present invention:

[0021] One of the technical advances is to overcome the inherent defect of limited contact area of ​​single worm teeth and greatly increase the contact area and number of teeth between the worm wheel and the worm. Another technical advance is to creatively provide a flexible worm mechanism that can compactly and effectively realize the torque transmission between the bent worm and the turbine.

[0022] The key technology of the present invention is:

[0023] The worm wheel is creatively driven by a bendable flexible worm to achieve high torque output of the turntable.

[0024] Specific content of the invention:

[0025] The zero-backlash flexible worm-type worm gear reducer includes three major components: a flexible worm, a worm wheel, a housing and a supporting component; the flexible worm is a (slender) spiral structure with a length-to-diameter ratio greater than 5 (as the diameter of the worm inner shaft decreases and the worm tooth wall is appropriately thinned, it will have a smaller bending moment, and it is easy to be bent and has better recovery elasticity; due to the continuous spiral structure, the flexible worm can withstand a larger torsional moment, and due to the continuous worm inner shaft, the flexible worm can also withstand greater tension and pressure; the original state of the flexible worm is straight, and it is bent into an arc shape during use;); the housing includes an upper housing and a lower housing; the supporting component includes end bearings or a middle retaining bearing is installed to enable the worm to obtain greater mechanical strength; the worm wheel includes a worm wheel disc (power output shaft) and a worm wheel helical tooth (referred to as worm tooth).

[0026] Assembly relationship: a vertical driving relationship is formed between the worm wheel and the flexible worm; the housing and the supporting components are used to install and fix the flexible worm and the worm wheel; the supporting component can be integrated with the housing, or include an independent bearing seat (fixed on the housing); in particular, the end bearing or the middle retaining bearing (including the worm wheel) as the supporting component constrains the flexible worm, and firmly grasps the end shaft and the middle section of the flexible worm, so that the axis of the flexible worm is forcibly bent into an arc shape, and the orientation of the end shaft is the tangent direction of the axis (the end bearing needs to withstand a large bending force and moment, and double-row rollers or double bearings can be used); in maintaining the arc shape of the flexible worm, in addition to using the end bearing, the middle retaining bearing can also be used or installed to complete it; the end bearing fixed on the housing is used to bend and maintain the arc shape of the flexible worm, and the direction of the end shaft axis is along the tangent direction of the circumference of the worm wheel, and the angle between the two end shaft axes is equal to the center angle corresponding to the arc shape of the flexible worm.

[0027] Working principle of zero backlash flexible worm gear reducer:

[0028] The essential difference between the present invention and the conventional worm gear reducer is that the bendable flexible worm bends and wraps the worm wheel, so that a larger number of teeth of the flexible worm are in contact with the worm wheel.

[0029] Further: the spiral teeth of the flexible worm gear are single-start or multi-start as mentioned above. The single-start is conducive to a large reduction ratio, while the multi-start has a smaller reduction ratio but improves the load capacity.

[0030] The technical progress of the present invention: the improved worm gear reducer will well overcome the defect of insufficient system rigidity; at the same time, the unique close contact force between the flexible worm and the worm wheel will be able to dynamically maintain high precision for a long time; and the improvement also brings the advantages of long life and miniaturization. [Drawings]

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

[0032] [ Figure 1 ] Schematic diagram of a zero-backlash flexible worm gear reducer.

[0033] [ Figure 2 ] Schematic diagram of the explosion of a zero backlash flexible worm gear reducer.

[0034] [ Figure 3}Schematic diagram of the elastic function of the flexible worm.

[0035] [ Figure 4 ] Schematic diagram of the structural parameter characteristics of the flexible worm.

[0036] [ Figure 5 ] Illustration of the specific installation position of the middle retaining bearing.

[0037] Description of the numbers in the figure:

[0038] 1 Worm gear

[0039] 1-1 Worm gear (power output disc)

[0040] 1-2 Worm gear helical gear

[0041] 1-3 Turbine axis

[0042] 2 Flexible worm

[0043] 2-1 spiral teeth

[0044] 2-2 Worm end shaft (power input shaft)

[0045] 2-3 Worm axis

[0046] 2-4 Middle axis

[0047] 2-5 worm inner shaft

[0048] 2-6 Worm tooth wall

[0049] 2-7 Inner shaft axis

[0050] 3 Shell and support parts

[0051] 3-1 Upper shell

[0052] 3-2 Lower shell

[0053] 3-3 Worm shaft hole

[0054] 3-4 end bearings

[0055] 3-5 Middle retaining bearing

[0056] 3-6 Worm gear shaft hole

[0057] [Implementation Case]

[0058] like Figure 1 , Figure 2 , Figure 3 and Figure 4 Shown:

[0059] The zero backlash flexible worm type worm gear reducer includes three major components: a flexible worm (2), a worm wheel (1), a housing and a supporting component (3); the housing generally includes an upper housing (3-1) and a lower housing (3-2); the supporting component includes an end bearing (3-4); the worm wheel includes a worm wheel disc (1-1) extending from a worm wheel shaft hole (3-6) as a power output, and worm wheel helical teeth (1-2) (also called worm teeth).

[0060] from[ Figure 4] It can be seen from the characteristic diagram of the structural parameters of the flexible worm that as the diameter of the worm inner shaft (2-5) decreases and the worm tooth wall (2-6) is appropriately thinned, the worm will have a smaller bending moment and will be easier to bend and have better elastic recovery. After bending, the inner shaft axis (2-7) is in a bent state. Since the flexible worm has a continuous spiral structure, under the constraints of the inherent characteristics of steel that is difficult to compress and stretch, the flexible worm can withstand a larger torsional moment. Furthermore, since the flexible worm has a continuous worm inner shaft (2-5), the flexible worm can also withstand a larger axial pressure and tension.

[0061] Assembly relationship: a vertical driving relationship is formed between the worm wheel (1) and the flexible worm (2); the housing and the support component (3) are used to install and constrain the flexible worm and the worm wheel; the support component can be integrated with the housing, or an independent bearing seat (the bearing seat is fixed on the housing); the end bearing (3-4) as the support component will constrain the flexible worm, and force the worm end shaft (2-2) of the flexible worm to extend from the worm shaft hole (3-3) of the housing, so that its axis is forcibly bent into an arc shape, and the orientation of the end shaft (2-2) is the tangent direction of the worm axis (2-3) (the end bearing needs to withstand a large bending force and moment, and a double row of rollers or double bearings can be used).

[0062] The working principle of the zero-backlash flexible worm gear reducer is essentially different from that of a conventional worm gear reducer in that the flexible worm (2) is bendable and can wrap around the circumference of the worm wheel (1) under the support of the end bearings (3-4), and make the worm wheel helical teeth (1-2) and the spiral teeth (2-1) mesh with each other; thus, the flexible worm has a larger number of teeth in contact with the worm wheel.

[0063] from Figure 3 It can be seen that the elastic function of the flexible worm is as follows: the flexible worm (2) is an elastic structure with a length-to-diameter ratio greater than 5, a slender worm, and the number of turns of the spiral teeth (2-1) is also relatively large (often up to dozens of turns); the turbine axis (1-3) that has not yet been installed is straight and will only bend when subjected to a bending moment; it is easy to bend when the diameter of the worm inner shaft (2-5) of the flexible worm (2) is appropriately reduced and the tooth wall is appropriately thinned.

[0064] like Figure 5 Shown:

[0065] A middle shaft (2-4) is provided in the middle section of the worm and is processed into a shaft shape. The installation of a middle retaining bearing (3-5) can increase the mechanical strength of the flexible worm. The position of the worm wheel (1) and the end bearing (3-4) is similar to Figures 1 to 4 same.

Claims

1. A zero backlash flexible worm type worm gear reducer, comprising three major components: a flexible worm, a worm wheel, a housing and a support component; the assembly relationship is: the housing and the support component are used to fix and install the flexible worm and the worm wheel; the worm wheel axis of the worm wheel and the worm end shaft of the flexible worm are in a vertical driving relationship; the working principle of the zero backlash flexible worm type worm gear reducer: the flexible worm is bent and wrapped around the worm wheel, and a large number of teeth are in contact with the worm wheel, and has a large strength and reduction ratio; its characteristics are: The flexible worm is a slender spiral structure with a length-to-diameter ratio greater than 5, which is resistant to torsion, compression or tension, but has bending elasticity. It is straight in its original state, and the axis of the flexible worm in use is in the shape of a curved arc. The arc shape of the flexible worm is bent and maintained using end bearings fixed on the housing. The direction of the end shaft axis is along the tangent direction of the circumference of the worm wheel, and the angle between the two end shaft axes is equal to the center angle corresponding to the arc shape of the flexible worm.

2. The flexible worm according to claim 1, characterized in that: The spiral teeth of the flexible worm gear are single-start or multi-start as mentioned above. The single-start is conducive to a large reduction ratio, while the multi-start has a smaller reduction ratio but improves the load capacity.

3. The flexible worm according to claim 1, characterized in that: In order to maintain the arc shape of the flexible worm, in addition to using the end bearings, a middle retaining bearing can also be used or installed.

Images