The strength of the double arc gear, whether it is the contact strength of the tooth surface or the bending strength of the gear teeth, is much higher than that of the involute gear and the single arc gear. The gear shaft, especially the stepped double arc gear, has better performance. In terms of processing technology, only one hob with convex and concave tooth profiles is required to cut double arc gears. Only the length of the common normal line on the profile of the convex tooth is measured during measurement, so the measurement instrument and the calculation of the length of the common normal line are greatly simplified. Step-by-step double arc gears show good performance when used in high, medium and low-speed high-power power transmission with good machining accuracy.

The maximum pitch circle speed of the same external involute gear is about 220m/s, the number of revolutions is 100,000 revolutions per minute, the power is over 25,000kW, the gear diameter is up to 4.25m, and the tooth width is up to 1.25m. up to more than 280 tons. If the arc gear is used instead, it is expected to meet the requirements of small size, light weight, long life, low noise, large speed ratio and high efficiency.

Efforts are made to improve the manufacturing and installation accuracy, especially to strictly control the center distance deviation of the gear pair to ensure the correct contact position of the meshing tooth surface, so as to facilitate running-in, reduce noise, reduce vibration, prevent pitting and gluing, etc. Flexural strength to prevent tooth breakage is also important.

Include lubrication and cooling techniques in design and maintenance. Due to the ever-increasing demands placed on gear drives, sufficient attention must also be paid to the lubrication and cooling of the gears. Many lubricating oil additives that have been successfully researched can effectively prevent gear failure and prolong service life. In terms of cooling technology, the method of flushing away the heat of the gear can be adopted, or an effective coolant can be used to greatly reduce the amount of lubricating oil, which not only saves the lubricating oil, but also reduces the volume of the gear device.

Gear shaft assembly

Research to improve the material of gears. According to our country's resource bar research, the alloy steel and nickel-free alloy steel of silicon, manganese, boron, titanium and rare earth elements are used to save nickel instead of nickel and prolong the life of circular arc gears. In addition, the purity of the material has a great influence on the strength of the gear, so it is necessary to develop non-destructive testing technology to ensure the purity of the material.

The damage form of the arc gear is related to the load condition of the gear. For example, light-loaded and medium-loaded gears (about 20-60% of the maximum rated allowable torque), gears with such loads are used in a relatively large amount, and their main damage form is tooth surface wear (there are also individual tooth surfaces. pitted). Heavy-duty gears (approximately equivalent to 80-100% of the maximum rated allowable torque), such loaded gears, some often run at full load. Some are full load part of the time, and the rest are moderate or full load operation. The main damage forms are tooth surface pitting, fatigue fracture and tooth surface wear. If there is a sudden impact load on the gear, the main damage form is the gear tooth fracture, or the gear tooth produces a slight crack, which leads to the premature fatigue fracture of the gear tooth. It can be seen from this that for double arc gears requiring long service life and slight or no impact, if the main purpose is to prevent fatigue pitting corrosion on the tooth surface, a larger full tooth height coefficient can be considered in the design, so as to obtain a larger The contact arc length is longer, which is beneficial to improve the contact strength. For gear transmissions with greater requirements on bending strength, short-toothed double-arc gears can be considered when designing.

For the heat treatment of double arc gears, the trial production and use of hardened double arc gears have been carried out at home and abroad, which has further improved the life of double arc gears, and is also a development trend that should be paid attention to in the future. New technologies for gear heat treatment are developing rapidly, such as multi-element co-infiltration, dual-frequency induction quenching, mixed treatment methods (such as nitriding or carburizing first, then induction quenching or rotary flame quenching), etc. Hardened layer depth, and residual stress is small. At the same time, it also improves the corrosion resistance during nitriding, enhances the fatigue strength of the tooth surface, and reduces the softening tendency when the temperature increases, and the hardness of the tooth surface is higher than that of the single heat treatment method. The above shows that the new heat treatment technology is of special importance. With improved material and heat treatment quality, the life of gears can be greatly extended. The lifespan of gears in my country has increased by more than five times compared with more than ten years ago, and may increase even more in the near future.

Regarding the trial production and use experience of the step-type double arc gear with hard tooth surface, it is tentatively believed that the nitriding hardness of the pinion can be controlled at about HRC 55; the quenched and tempered hardness of the large gear should preferably not be lower than HB280.

Production practice and experimental studies have proved that for medium and high-speed gear transmission, it is best to use double arc gears with larger tooth heights, because when the tooth heights are larger, the flexibility of the teeth can be increased and the noise can be reduced.