(1) Cylindrical gear transmission
For parallel shaft transmission, the general transmission ratio can range from 8 to a maximum of 20 in a single stage. In two stages, it can be up to 45, with a maximum of 60. The third level can range from up to 200, with a maximum of 300.
The transmission power can reach 100,000 kilowatts and the speed can reach 100,000 revolutions per minute (r/min), with a peripheral speed of up to 300 meters per second (m/s).
The single-stage efficiency ranges from 0.96 to 0.99.
The spur gear drive is suitable for medium and low-speed transmissions.
The helical gear drive operates smoothly and is ideal for medium to high-speed transmissions.
The herringbone gear drive is ideal for transmissions that require high power and high torque.
There are three types of meshing gears:
- External meshing gear, where two external gears drive the transmission and the steering of the two wheels is reversed.
- Internal gear transmission, where an internal gear and a smaller external gear engage, and the steering of the two wheels is the same.
- Rack and pinion drive, which can convert the rotation of the gear into linear movement of the rack or vice versa.
(2) Bevel gear transmission
This transmission is used for transferring power between intersecting shafts. The single-stage transmission ratio can range from 6 to a maximum of 8, with an efficiency that typically falls between 0.94 and 0.98.
Straight bevel gear transmissions can deliver up to 370 kW and have a peripheral speed of 5 m/s. Helical bevel gear transmissions offer smooth operation and a high gear carrying capacity, but are challenging to manufacture and have limited applications.
The curved bevel gear drive operates smoothly and has a transmission power of 3700 kW, with a peripheral speed exceeding 40 m/s.
(3) Hyperboloid gear transmission
Used to transmit power between the axles.
The single-stage transmission ratio can reach up to 100 with a maximum of 10, and the transmission power can reach 750 kW. The transmission efficiency is typically in the range of 0.9 to 0.98, and the peripheral speed can reach 30 m/s.
The axial offset allows for the avoidance of pinion cantilever mounting.
It is widely used in automotive and tractor transmissions.
(4) Helical gear transmission
For the intermeshing transmission, the transmission ratio can reach a maximum of 5. However, it has a low load capacity and experiences significant wear, making it a less common application.
(5) Worm drive
The main form of the staggered shaft drive has an axis stagger angle that is typically 90°.
The worm drive has a high transmission ratio, ranging from 8 to 80 for single stage and up to 1500 for transmitting motion.
It can transfer power up to 4500 kW and has a worm speed of up to 30,000 revolutions per minute (r/min).
The peripheral speed can reach 70 meters per second (m/s).
While the worm drive operates smoothly and accurately, it has a low transmission efficiency when self-locking, typically less than 0.5.
The worm gear has a large amount of sliding between the tooth surfaces, which leads to higher heat generation and lower transmission efficiency, typically between 0.45 and 0.97.
(6) Arc gear transmission
A gear transmission has a tooth profile with a convex and concave arc.
When operating without a load, the two tooth profiles have point contacts.
During the meshing process, the contact points move along the axis direction and the degree of longitudinal coincidence is greater than one to ensure a continuous transmission.
This type of transmission is characterized by high contact strength and load-bearing capacity, the easy formation of an oil film, no root cutting, uniform tooth surface wear, and good performance during operation.
However, it is highly sensitive to the center distance, cutting depth, and helix angle, so high accuracy is required in manufacturing and installation.
(7) Cycloidal gear transmission
A gear train has a tooth profile with a cycloid.
The tooth surfaces of the transmission have minimal contact, providing good wear resistance and no root cutting. However, high precision is required in manufacturing and even small errors in the center distance can significantly impact its performance.
This type of gear train is typically used only in watches and meters.
(8) Planetary gear transmission
Gear Drive with Moving Axis
There are several types of planetary gears and their performance varies greatly. Hence, it is crucial to make an informed decision while choosing the type based on the working conditions.
The commonly used types include ordinary planetary transmissions with components such as sun gears, planetary gears, internal gears, and planet carriers, planetary gears with minimal tooth differences, cycloidal pin drives, and harmonic drives.
The planetary gear transmission typically comprises of parallel shaft gears that are compact and lightweight.
The input and output axes can be aligned in a single line.
The usage of this technology is rapidly increasing and becoming more widespread.
