Is The Tooth Top Height Coefficient A Variable Value Or A Fixed Value

The tooth top height coefficient is a variable or fixed value that depends on the type, design requirements, and purpose of the gear.

Firstly, the tooth top height coefficient (usually represented by the symbol ha *) is the ratio of the gear tooth top height to the modulus, i.e. h α/m. It reflects the rationality, tightness, and smoothness of the gear tooth structure, directly affecting the reliability, smoothness, and transmission efficiency of gear operation.

The value of the tooth top height coefficient varies for different gears:

Under normal tooth system, when the modulus of the gear is greater than 1mm, the tooth top height coefficient is usually 1 and the top clearance coefficient is 0.25.

When the modulus is less than 1mm, the tooth top height coefficient remains 1, but the top clearance coefficient increases to 0.35.

For short constant tooth gears, the tooth top height coefficient is reduced to 0.8, while the top clearance coefficient is 0.3.

However, in certain specific situations, such as the design of long tooth gears in modern sedan transmissions, the tooth top height coefficient may be greater than 1 to increase overlap and improve the performance of the gears in terms of strength, noise, dynamic load, and vibration. Although this design has advantages, it may also bring problems such as relatively high sliding speed, easy undercutting, or tooth tip sharpening.

Therefore, when selecting the tooth top height coefficient, it is necessary to comprehensively consider factors such as the transmission efficiency, noise, vibration, and applicable range of the gear. The tooth top height coefficient can be a fixed value or a value that varies within a certain range, depending on the design requirements and usage of the gear.

What is the tooth top height system?

The tooth top height system is not a directly mentioned term, but I can provide you with a detailed explanation based on the concept of "tooth top height".

Firstly, the tooth tip height is a mathematical term that specifically refers to the radial distance between the indexing circle and the tooth tip circle of an involute cylindrical gear. Simply put, when we observe a gear, the tooth tip height describes the vertical distance between the tooth tip and the indexing circle.

The calculation of tooth top height is usually closely related to other parameters of the gear, such as modulus, pressure angle, and number of teeth. For example, in some cases, the tooth top height can be calculated by combining the common normal height and tooth height, where the common normal height is the distance from the intersection point of the common normal and tooth top of two gears to the centerline of the gear, and the tooth height is the distance from the tooth top to the tooth valley.

As for the role of tooth tip height, it plays an important role in gear transmission. Especially for helical gears, the size of the tooth tip height directly affects the accuracy and noise of the gear. Under high-speed rotation and heavy load conditions, the mismatch of tooth tip height may lead to excessive bearing force, thereby reducing the efficiency of the transmission system.

In summary, although "tooth top height system" is not a directly mentioned term, we can understand it as a comprehensive consideration involving tooth top height calculation and influence. In practical applications, the correct selection and design of tooth top height is crucial for ensuring the performance and lifespan of gear transmission.