Gears are mechanical parts with teeth that can mesh with each other to transmit motion and power in mechanical transmission. Gear transmissions stand out due to the accuracy of their gear ratio, which makes them perfect for precision machinery.
What is A Gear?
Gears are mechanical parts with teeth that can mesh with each other. It uses the teeth of two gears to mesh with each other to transmit motion and power in mechanical transmission. Among all mechanical transmissions, gear transmission is the most widely used and can be used to transmit motion and power between two shafts that are not far away from each other.
Classifications of Gears
There are many kinds of gears, and the most common classification method is according to the gear shaft. Generally, gears are divided into three categories: parallel axis, intersecting axis, and staggered axis.
Parallel Shaft Gears
Including spur gears, helical gears, internal gears, racks and helical racks, etc.
Intersecting Shaft Gears
There are straight bevel gears, spiral bevel gears, zero-degree bevel gears, etc.
Staggered Shaft Gears
There are staggered shaft helical gears, worm gears, hypoid gears, etc.
What is A Gear Transmission?
Gear transmissions are mechanisms composed of two toothed wheels that mesh tooth by tooth, and when involving spur gears, they are called bull gear (the larger gear) and pinion (the smaller gear). One acts as the drive or driving gear and the other one as the driven gear.
Gear transmissions stand out due to the accuracy of their gear ratio, which makes them perfect for precision machinery.
Features of Gear Transmission
Efficient
Among the commonly used mechanical transmissions, the gear transmission efficiency is the highest, and the closed transmission efficiency is 96%~99%, which has great economic significance for high-power transmission.
Compact
The space size required for belt and chain drive is small.
Stable Transmission Ratio
Stable transmission ratio is often the basic requirement for transmission performance. Gear transmission is widely used because of this feature.
Reliable Work and Long Life
The gear transmission is designed and manufactured correctly and reasonably, and is well maintained. The operation is very reliable and the service life can be as long as ten or twenty years. This is especially important for vehicles and machines working in mines.
However, the manufacturing and installation precision are required for gear transmission. The price is relatively high, and it is not suitable for occasions where the transmission distance is too far.
Classification of Gear Transmission
Gear transmission can be divided into cylindrical gear transmission, bevel gear transmission, non-circular gear transmission, rack transmission and worm transmission according to the shape of the gear.
Cylindrical Gear Drive
A gear transmission used to transmit motion and power between parallel shafts. According to the relative relationship between the gear teeth and the gear axis, the cylindrical gear transmission can be divided into three types: spur gear transmission, helical tooth cylindrical gear transmission, and herringbone tooth cylindrical gear transmission.
The transmission power and speed of the cylindrical gear drive have a wide range of applications, the power can be from less than one thousandth of a watt to 100,000 kilowatts, and the speed can be as low as 300 meters per second.
The meshing characteristics can be seen from the formation process of the tooth profile surface. When the involute spur gear is meshed, the contact line of the tooth profile surface is a straight line parallel to the axis. During the meshing process, the entire tooth width enters and exits meshing at the same time. The force is also suddenly added or removed, so the transmission stability is poor, and the impact and noise are loud.
Bevel Gear Drive
Bevel gear transmission is a gear transmission between intersecting shafts composed of a pair of bevel gears, also known as bevel gear transmission. According to the shape of the tooth line, the bevel gear transmission can be divided into straight bevel gear transmission, helical bevel gear transmission, and curved bevel gear transmission, among which straight and curved teeth are widely used.
Rack Drive
The transmission structure of gear and rack, the rack is divided into spur rack and helical rack, which are paired with spur gear and helical gear respectively; the tooth profile of the rack is straight rather than involute in terms of surface, it is a plane, which is equivalent to an infinite cylindrical gear with an indexing circle radius.
Worm Drive
It is a transmission that transmits motion and power between two axes interlaced in space. The angle between the two axes can be any value, and the commonly used one is 90°.
The worm drive is composed of a worm and a worm wheel, and the worm is generally the driving part. Like threads, worms are divided into right-handed and left-handed, which are called right-handed worms and left-handed worms, respectively. The worm with only one helix is called a single-head worm, that is, the worm rotates once, and the worm wheel rotates one tooth. If there are two helixes on the worm, it is called a double-head worm, that is, the worm rotates once, the worm wheel turns over two teeth.
According to the tooth profile curve, it can be divided into involute gear transmission, cycloid gear transmission, and arc gear transmission. A transmission consisting of more than two gears is called a gear train. Gear transmission can be divided into ordinary gear transmission and planetary gear transmission according to whether there are gears with axial movement in the gear train. The gears with axial movement in the gear train are called planetary gears.