The main disadvantages of arc gears in high-speed transmission:
1. It is difficult to process and more costly
The tooth profile accuracy of arc gears has a great impact on high-speed performance, but its processing technology is much more complicated than involute gears:
Dependence on special equipment : special arc gear milling cutters and grinders (such as Y3180 arc gear milling machine), and processing equipment that cannot be used for involute gears, the equipment investment cost increases by 50% to 100%.。
Strict accuracy control : The arc tooth profile 'tooth arc radius''tooth drum volume' of the arc tooth profile needs to be strictly matched (small deviation at high speed will cause a sudden increase in contact stress), the processing tolerance needs to be controlled at IT5~IT6 levels (the high-speed stage of involute gears is usually IT6~IT7 levels), the machining working hours are increased by 30%~60% , and the final gear manufacturing cost is 40%~80% higher than that of involute gears。
2. The installation has extremely high neutral requirements and poor fault tolerance
The installation deviation (parallelism, coaxiality) of the gears in high-speed transmission will be amplified, while the arc gears have a lower tolerance for installation accuracy:
Strong contact sensitivity : If the parallelism deviation between the input shaft and the output shaft exceeds 0.02mm/m , or the coaxial deviation exceeds 0.01mm , the contact line of the arc gear will change from 'full tooth width contact' to 'local contact', and the contact stress will instantly increase by 2 to 3 times , which can easily lead to early wear or glued teeth.
Installation and debugging are complex : Use precision laser centering instruments (such as Pretzt laser centering instruments) to be installed and calibrated. The debugging time is 2 to 3 times longer than involute gears . If the shaft system deformation occurs during later maintenance (such as high-speed vibration causing bearing wear), it needs to be re-centered, making maintenance more difficult.
3. Lubrication requirements are harsh and susceptible to oil contamination
The performance of lubricant at high speed directly determines the life of the gear, and the requirements for lubricant of arc gears are much higher than those of involute gears:
Oil viscosity and cleanliness sensitivity : Extreme pressure industrial gear oil with high viscosity index (VI>140) and low coagulation point (<-20℃) is required, and solid particulate pollutants in the oil must be controlled below NAS level 8 (involute gears are usually NAS level 10); if oil is contaminated, the linear contact of the arc gear is easily 'wrapped with impurities', which leads to scratching the tooth surface 3 to 5 times higher than that of the involute gears。
The cost of lubrication system is high : it is necessary to provide a high-efficiency filter (such as a 10μm precision oil return filter) and an oil temperature control system (such as a forced cooler), and the cost of the lubrication system is increased by 40% to 60%.。
4. Applicable scenarios are limited and interchangeability is poor
The design characteristics of arc gears make it difficult to generalize, limiting its application range:
The main non-standard design is : the tooth profile parameters of arc gears (such as arc radius and number of teeth) need to be customized according to the specific transmission conditions (speed, load, center distance). There is no unified 'standard module series'. Products from different manufacturers cannot be exchanged. The later replacement of spare parts must rely on the original manufacturer, with a long cycle (usually 4 to 8 weeks) and a high cost.
Not suitable for small transmission ratio scenarios : When the transmission ratio is <3, the tooth profile overlap of the arc gear will be significantly reduced (<1.2), the advantage of transmission stability disappears, and 'tooth top interference' is prone to occur, so it is more suitable for high-speed transmission with i≥3, while involute gears are more flexible in small transmission ratio scenarios.
