Spur gears, also known as cylindrical gears, are the gears most commonly used in gear units. Their main feature is a relatively simple design. Smaller or larger numbers of spur gears can be installed in gear units. These may require few moving parts, depending on the specific application and requirements – in contrast, for example, to ring gears in planetary gear units or worm gear units.
Spur gears have evenly spaced teeth around their circumference for intermeshing with other gears. Gear combinations for spur gears can be produced in different versions and sizes which are called modules.
A spur gear is ultimately used in a cylindrical gear unit. The simplest and most common design is the single-stage gear unit in which two gears are mounted on a shaft. When more gears and intermediate shafts are added, the result is a multistage gear unit.
Gears are also classified by their tooth angle – the pattern of the teeth can be straight, helical, or even double helical. In the case of the straight version, 1 to 3 teeth are normally engaged at one time. To transmit sufficient power, a tooth must always mesh with its counterpart.
Often, however, helical gearing is used – for example, to reduce noise. The meshing of spur gear is much smoother and the length of the path of contact is longer.
Helical gears have one disadvantage: Lateral forces are generated that have to be structurally supported by bearings in the cylindrical gear unit.
Double helical gearing, on the other hand, has a relatively complex design and requires a more sophisticated manufacturing process. In this case, two helical gears with different helix angles are used. Reasons for using helical gears include quieter running of the cylindrical gear and a higher torque transmission. Another benefit is the fact that lateral forces are eliminated, which also eliminates the need for additional bearings. In addition, their tooth strength and pitting resistance are slightly higher than that of the straight-tooth version, which can also be a major contributing factor to higher torque transmission.
What’s most important about cylindrical gear units is the gearing design. Existing programs can be used to precisely calculate beforehand whether the gear unit achieves the necessary transmission rate. These calculation formulas are extremely reliable and have been validated many times by practical experience.
Feel free to contact us if you have any questions about spur gears or cylindrical gear unit modules. We will be happy to help!