What are the types of gears & How to Choose the Right Gears

Gears are components that are arranged in a sawtooth shape and usually appear in a circular or circular-like structure. Gears are key mechanical components that can precisely mesh with their teeth to achieve efficient power transmission and improve motion efficiency. They can freely change the direction of power at any time, and can also accurately change the speed and torque by themselves to further achieve long-distance transmission. It is not an exaggeration to say that it is an indispensable "power bridge" in modern mechanical equipment.

So, do you know what are the main types of gears? What has been your experience in selecting the right ones? JLCMC will help you understand better through its products.

What are the types of gears?

The common types of gears are spur gears, helical gears, herringbone gears, worm and worm wheels, internal gears, as well as racks and pinions. These only account for the main part of the gear category. In fact, there are more types of gears for special purposes, which will not be described here one by one.

1. Spur gears are composed of hubs, ring gears and racks. The hub is a component fixed on the shaft. The ring gear undertakes the main working part, and the rack cooperates with the spur gear for transmission. Its gear teeth are parallel and meshed with the axis, so the structure is simple, the transmission is stable and efficient, and the load-bearing capacity is very strong. It is particularly suitable for scenes requiring high-speed transmission. The disadvantages of simple structure are also obvious. Noise and vibration are two major problems that need to be paid attention to. It is usually widely used in industrial equipment that requires high-speed transmission, such as automobile gearboxes and machine tool transmission systems.

Fig. 1 Spur Gears

2. Helical gears are composed of helical racks and helical gears. Because their gears are inclined to the axis, they are called helical gears. It can be said that helical gears are iterative versions of spur gears. The design optimizes the shortcomings of spur gears, making the meshing process smoother, and greatly reducing noise and vibration. In addition to the advantages of spur gears, they also have the characteristics of compact structure, large overlap and cross-axis transmission, which are suitable for high-speed and high-power transmission under various working conditions.

Fig. 2 Helical Gears

3. The appearance of herringbone gears is to eliminate the lateral force generated by the helical gears on the shaft. The structure consists of two symmetrical helical gears in opposite directions to achieve mutual offset of forces. It can be seen that helical gears are not without disadvantages. Herringbone gears not only inherit the advantages of helical gears, but also magnify them on the original basis. They are also suitable for occasions with high transmission performance, such as transmission of heavy machinery and rolling mills.

Fig. 3 Herringbone Gears

4. Worm and Worm Wheels are two mechanical parts. The worm is similar to a screw and has one or several helical teeth. It can also be subdivided into ZA worm, ZI, ZN and ZK worm. When meshing with the worm wheels, it can form a gear of a staggered axis gear pair. When meshing, it can achieve a large reduction ratio transmission and has a self-locking function under certain conditions. This tooth design structure makes the transmission ratio between the turbine and the worm large and the structure compact, with relatively low noise and vibration. It is commonly used in self-locking mechanisms, elevators, reducers and other occasions that require a large reduction ratio transmission.

Fig. 4 Worm and Worm Wheels

5. The combination of internal gears is quite special. The pinion is located inside the large gear. The pitch of the pinion is arc-shaped, and then it is embedded in the tooth space of the large gear to achieve internal meshing transmission. Internal gears can also be subdivided into two types: internal meshing spur gears and internal meshing helical gears. The advantages are compact structure, large transmission torque and high precision. It is mostly used in precision and complex devices, and plays an important role in heavy industry, aircraft engines, aircraft reducers, and automobile four-wheel drive systems.

Fig. 5 Internal Gears

6. Rack and Pinion, the rack is a special gear with teeth distributed on the bar body, which can also be subdivided into spur rack and helical rack, and the gear is the gear. The combination between them also has unexpected effects. When the rack and the circular gear (pinion) are meshed, the mutual conversion of linear motion and rotational motion can be realized. The characteristics of the rack make the combination with the gear also have the characteristics of splicing stroke, and almost any length of stroke can be obtained to achieve precise positioning. It is widely used in occasions such as automobile steering systems and machine tool feed mechanisms that require linear and rotational motion conversion.

Fig. 6 Rack and Pinion

How to choose the right gear

With various types of gears available, including spur, helical, and worm gears, understanding the specific requirements of your application is essential. We will explore key factors to consider when selecting gears, helping you make informed decisions that enhance performance and durability.

Selection of Gear Materials

The selection of gear materials is diverse, including steel, aluminum, plastic, bronze, aluminum alloys, and cast iron. Typically, we determine the appropriate material based on its application scenario and load-bearing capacity. Prioritizing the comprehensive consideration of these material characteristics will help choose the most suitable gear to meet various operational needs.

Calculate transmission requirements

You need to first understand the basic requirements of the current transmission system, such as transmission ratio and torque. Calculate the relationship between input and output speeds to obtain the current required transmission ratio, and then understand the maximum torque that the selected gear can withstand under the workload, and basically there will be no big problems.

Fig. 7 Gear ratio calculation formula

Adapt to the working environment

Evaluate the comprehensive factors such as temperature, humidity, corrosive substances in the current working environment in advance, and use this as a reference to select suitable gear materials and protection levels. This rating system follows the international standard IEC 60529, usually represented by the IP code. The IP code consists of the IP letter and two numbers. The first number represents the protection level against solid substances, and the second number represents the protection level against liquid substances. When the protection problem of the gear is determined, consider whether it is necessary to control noise and vibration.

Determine accuracy and service life

Select the appropriate gear accuracy level according to the accuracy requirements of the gear in the use scenario. According to the ISO gear grade standard, it can be divided into 1-12 levels, among which level 12 has the lowest accuracy. If the accuracy problem is not handled properly, it may cause noise, vibration, wear and poor transmission effect in the transmission system. The service life of the gear can be set based on the years of use, working hours or other relevant indicators, and the best one can be selected considering the cost and maintenance issues.

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