The transmission of precision gears is usually referred to as a timing drive; it replaces the usual timing chain with straight cut gears. When the gears turn with the rotation of the engine, the teeth of the gears mesh together, which keeps the engine in time.
Geared equipment means that two gears are required to operate. The two gears are tangential and the drive gear receives the force from the PTO. The drive gear transmits power to the driven gear. Gearing systems are moving towards lighter weight and longer lifespans, especially in the aerospace industry, where traditional gearing doesn't work well under harsh operating conditions. Therefore, gear transmission has special regulations and basic requirements.
1. The transmission should be stable. It is stipulated that during the transmission process of precision gears, the instantaneous gear ratio should always be strictly maintained, otherwise the driving wheel rotates at a constant speed and the driven wheel rotates fast and slow, which will cause shock, vibration and noise, affecting the quality of the transmission. Since the gear adopts a reasonable tooth profile (usually involute, cycloid and circular arc are used, involute is the most commonly used), the instantaneous gear ratio is guaranteed to remain unchanged. In this way, the transmission can be maintained smoothly and the working accuracy of the gears can be improved, so as to be suitable for high-precision and high-speed transmission.
2. Better bearing capacity. It is stipulated that precision gears must have sufficient damage resistance to transmit large power, and also need to have a long service life and a small structure size.
In order to meet the above two basic requirements, it is necessary to clearly put forward corresponding regulations on many aspects such as the shape of the transmission gear, the material of the gear, the processing of the gear shaft, the heat treatment process, and the quality of the assembly.
Are the materials used in the design of precision gears consistent with the selection of large and small gears? Not at all. Taking the reducer as an example, the gear ratio of the standard gear is usually about 3, and the transmission gears of the large and small gears are almost the same, so the same material can be selected. For example, for gears with hard tooth surfaces, it is usually good to choose 20CrMnTi, and choose standard carburizing, high frequency surface quenching heat treatment specifications, and grinding teeth. There are individual gears with too large gear ratios, which can slightly improve the material and surface strength of the pinion, because the actual working time of the transmission gear of the large gear is only a fraction of the time of the pinion, and the pinion is more prone to damage.