The advantages and disadvantages of harmonic reducer

Time:2020-06-10 02:35:25

Harmonic gear reducer is a deceleration device, composed of three basic components: fixed internal tooth rigid wheel, flexible wheel (that is, the elastic thin-walled cup whose base body is connected with the driven shaft "the generatrix at the beginning of the flexible wheel Make a ring gear"), and a wave generator that radially deforms the flexible wheel.


Harmonic reducers are used in aviation, aerospace, energy, navigation, shipbuilding, biomimetic equipment, commonly used ordnance, equipment beds, instruments, electronic equipment, mining metallurgy, transportation, lifting equipment, petrochemical equipment, textile equipment, agricultural equipment, and medical Instruments and other aspects have been increasingly widely used, especially in the servo system with high dynamic performance, the use of harmonic drive shows its superiority. It transmits power from tens of watts to tens of kilowatts, but high-power harmonic gear drives are mostly used in short-term work. So what are the advantages of harmonic reducer? Let's take a look together below.


Composition structure

The harmonic gear reducer is composed of three main components: rigid wheel, flexible wheel, and wave generator. Among them, the wave generator is the active part, and one of the rigid wheel and the flexible wheel is the driven part. The fixed rigid wheel is a rigid internal gear, and the flexible wheel is a thin-walled cylindrical external gear that is easily deformed. They have a triangular (or involute) tooth shape, and the two have the same circumferential pitch, but the rigid wheel is more flexible than the flexible wheel. Several more teeth (usually two teeth). The wave generator consists of an elliptical disk and a flexible ball bearing, or a rotating arm with rollers on both ends. Usually the wave generator is the original moving body, one of the flexible wheel and rigid wheel is the driven body, and the other is the fixed part.


The main advantage

(1) The transmission speed ratio is large. The speed ratio range of single-stage harmonic gear transmission is 70~320, which can reach 1000 in some devices, and the multi-stage transmission speed ratio can reach more than 30,000. It can be used not only for deceleration, but also for increasing speed.


(2) High carrying capacity. This is because the number of teeth simultaneously meshed in the harmonic gear transmission is large, and the number of teeth simultaneously meshed in the double-wave transmission can reach more than 30% of the total number of teeth, and the flexible wheel uses high-strength materials, and the teeth are in surface contact with each other.


(3) High transmission accuracy. This is because the number of teeth simultaneously meshed in the harmonic gear transmission is large, and the error is averaged, that is, the multi-tooth meshing has a mutual compensation effect on the error, so the transmission accuracy is high. In the case of the same gear accuracy level, the transmission error is only about 1/4 of that of the ordinary cylindrical gear. At the same time, the radius of the wave generator can be changed by a small amount to increase the deformation of the flexible wheel so that the backlash is small, and even backlash-free meshing can be achieved. Therefore, the harmonic gear reducer has a small transmission backlash and is suitable for reverse rotation.


(4) High transmission efficiency and smooth movement. Due to the uniform radial movement of the flexwheel teeth during the transmission process, even if the input speed is high, the relative slip speed of the gear teeth is still extremely low (so it is a percent of the ordinary involute gear transmission -) Therefore, the gear tooth wear is small and the efficiency is high (up to 69%~96%). Since both sides of the gear are engaged in work when they are engaged and engaged, there is no impact and the movement is smooth.


(5) Simple structure, few parts and easy installation. There are only three basic components, and the input and output shafts are coaxial, so the structure is simple and the installation is convenient.


(6) Small size and light weight. Compared with the general reducer, when the output torque is the same, the volume of the harmonic gear reducer can be reduced by 2/3, and the weight can be reduced by 1/2.


(7) Can transmit motion to confined spaces. Taking advantage of the flexible characteristics of flexible wheels, this valuable advantage of wheel transmission is unmatched by other existing transmissions.




The main disadvantage

(1) The flexible wheel deforms periodically, thus generating alternating stress, making it prone to fatigue failure.


(2) The moment of inertia and starting torque are large, so it is not suitable for the tracking drive with small power.


(3) Cannot be used in the case where the transmission speed ratio is less than 35.


(4) Harmonic transmission using roller wave generator (free deformation wave), the instantaneous transmission ratio is not constant.


(5) Poor heat dissipation conditions.