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Harmonic gear speed reducer

The harmonic gear transmission constitutes:

It consists mainly of three basic components:

1.A rigid gear (rigid wheel) with an internal ring gear, which is equivalent to the center wheel in the planetary system;

2.A flexible gear (flexible wheel) with an outer ring gear, which is equivalent to a planetary gear;

3.Wave generator H, which is equivalent to a planet carrier.

As a gear reduction, it is usually used in the form of a wave generator active, rigid wheel fixed, and flexible wheel output.

  1. Harmonic gear unit principle:

1.The principle of the harmonic gearbox is that the wave generator H is a rod-shaped member which is provided with rolling bearings at both ends thereof to form a roller, which is pressed against the inner wall of the flexible wheel 1.

2.The flexible wheel is a thin-walled gear that can generate large elastic deformation, and the inner hole diameter is slightly smaller than the total length of the wave generator. Harmonic speed reducer’s wave generator is a member that causes the flexible wheel to produce a controlled elastic deformation.

  1. When the wave generator is inserted into the flexible wheel, the section of the flexible wheel is forced to change from the original circle to the ellipse, and the teeth near the two ends of the long axis are completely meshed with the teeth of the rigid wheel, and the ends of the short axis are near The teeth are completely disengaged from the rigid wheels.

4.The teeth of the other sections on the circumference are in a transitional state of engagement and disengagement. When the wave generator of harmonic gear drive continuously rotates in the direction shown, the deformation of the flexible wheel is constantly changing, and the meshing state of the flexible wheel and the rigid wheel is also constantly changed, by being engaged, meshed, engaged, disengaged, and then engaged... Repeatedly, the slow rotation of the flex wheel relative to the rigid wheel in the opposite direction of the wave generator H is achieved.

5.When working, the fixed wheel is fixed, the electric motor drives the wave generator to rotate, and the flexible wheel acts as the driven wheel, and the output rotates to drive the load movement. During the transmission process, the wave generator of harmonic gear drive turns one revolution, and the number of cycles of deformation at a certain point on the flex wheel is called the wave number, which is represented by n.

6.Commonly used are two waves and three waves. The double-wave transmission has a low flex wheel stress and a relatively simple structure, making it easy to obtain a large transmission ratio. Therefore, it is the most widely used one.

  1. ,Detailed explanation of the principle of harmonic gear transmission

1.When the harmonic generator is active, the cam rotates in the flexible wheel, forcing the elastic wheel and the thin-walled bearing to perform elliptical deformation motion (controllable elastic deformation), at which time the teeth of the flexible wheel enter during the deformation process. (Mesh) or exit (bite) between the teeth of the rigid wheel.

2.The flexible teeth at both ends of the long axis of the cam ellipse mesh with the internal teeth of the rigid wheel along the tooth height。

3.This is harmonic gear speed reducer’s meshing zone, generally about 30% of the teeth are in meshing state; the soft teeth and the rigid teeth at both ends of the elliptical short axis are completely disengaged (disengaged); the long and short axes of the harmonic generator are Between the different teeth of the flexible wheel, some gradually enter the teeth of the rigid wheel, in a semi-engaged state (biting); some gradually withdraw between the teeth of the rigid wheel, in the semi-detachment State (engaged)。

4.The harmonic generator of harmonic gear reduction continuously rotates in the flexible wheel, forcing the flexible wheel to produce continuous elastic deformation, and the four states of the engagement and engagement of the flexible tooth and the rigid tooth are reciprocated. Wrong tooth movement. The wrong tooth movement can change the high speed rotation of the input of the reducer to the low speed of the output ground.

For the harmonic gear transmission of the two-wave harmonic generator, when the harmonic generator rotates clockwise 1/8 of a week, the soft teeth and the rigid teeth become engaged by the original biting, and the disengagement becomes a bite. The biting becomes disengaged and the meshing becomes a biting. At this time, the flexible wheel rotates (angular displacement) by 1/4 tooth relative to the rigid wheel; similarly, when harmonic gear reducer’s harmonic generator rotates for another 1/8 week, the above process is repeated, when the flexible wheel rotates 1/2 tooth relative to the rigid wheel. When the harmonic generator turns over 1/2 week, the flexible wheel rotates one pitch with respect to the rigid wheel; when the harmonic generator rotates for one week, the flexible wheel rotates two pitches relative to the rigid wheel.

The harmonic generator continuously rotates, forcing the point on the flex wheel to change position continuously. At any point on the pitch circle of the flex wheel, along with the angular displacement of the harmonic generator, a symmetrical and harmonic is formed. -harmonic.

When working, the fixed wheel is fixed, the electric motor drives the wave generator to rotate, and the flexible wheel acts as the driven wheel, and the output rotates to drive the load movement.In the transmission process, the wave generator rotates once, and the number of cycles of deformation at a certain point on the flex wheel is called the wave number, which is represented by n. Commonly used are two waves and three waves. The double-wave transmission has a low flex wheel stress and a relatively simple structure, making it easy to obtain a large transmission ratio. At present, harmonic gear reducers in various countries are mostly in the form of dual-wave internal generators.

The flexible wheel and the rigid wheel of harmonic gear unit have the same circumference, but the number of teeth is not equal. Usually, the difference between the number of teeth of the rigid wheel and the flexible wheel is equal to the wave number, that is: Z2-Z1=n where z2 and z1 are the rigid wheel and the softness respectively. The number of teeth in the wheel.

When the rigid wheel is fixed, the generator is active, and the flexible wheel is driven, the transmission ratio of the harmonic gear motor is i=-z1/(z2-z1)

In the double-wave transmission, z2-z1=2, and the number of teeth of the flexible gear is large. The negative sign of the upper type indicates that the steering of the flex wheel is opposite to the steering of the wave generator. It can be seen that the harmonic gear reducer can obtain a large transmission ratio.

  1. Harmonic gear drive features:
  2. High reduction ratio

Single-stage coaxial can achieve a high reduction ratio of 1/30 to 1/320. The structure and structure are simple, but the high reduction ratio device can be realized.

  1. Small backlash

Unlike the meshing with ordinary gears, the backlash of harmonic speed reducer is extremely small, which is an indispensable element in the field of controllers.

  1. High precision

The multi-tooth meshes at the same time, and there are two 180-degree symmetrical gear meshes. Therefore, the gear pitch error and the cumulative pitch error have a relatively uniform effect on the rotation accuracy, so that the position accuracy and the rotation accuracy reach an extremely high level.

  1. Less parts and easy installation

The three basic components achieve high reduction ratios, and they are all coaxial, so the kit is easy to install and simple in shape.

  1. Small size and light weight

Compared with the conventional gear unit, harmonic gear reduction’s volume is 1/3 and the weight is 1/2, but the same torque capacity and reduction ratio can be obtained, achieving small size and light weight.

  1. High torque capacity

The flexible wheel material of harmonic gear speed reducer uses special steel with high fatigue strength. Unlike ordinary transmissions, the number of teeth engaged at the same time accounts for about 30% of the total number of teeth, and is a surface contact, so that the pressure applied to each gear becomes small, and a high torque capacity can be obtained.

  1. High efficiency

The gear teeth meshing portion of harmonic gear box is very small, which reduces the power loss caused by friction. Therefore, while achieving a high reduction ratio, high efficiency is maintained and the drive motor is miniaturized.

  1. Low noise

The gear teeth of harmonic gear drive meshing at a low speed and transmitting the balance of motion and power, so the operation is quiet and the vibration is extremely small.

  1. Harmonic gear motor application:

Harmonic gear unit in aviation, aerospace, energy, marine, shipbuilding, bionic machinery, common ordnance, machine tools, instruments, electronic equipment, mining and metallurgy, transportation, lifting machinery, petrochemical machinery, textile machinery, agricultural machinery and medical Instruments and other aspects are increasingly used, especially in high dynamic performance servo systems, the use of harmonic gear transmission shows its superiority. It delivers power from tens of watts to tens of kilowatts, but high-power harmonic gearing is often used for short-term work.