The pitch circle of synchronous belt pulley refers to two pure rolling circles made according to the transmission ratio, which will appear only after the gear is assembled.
The indexing circle of synchronous belt pulley is a geometric structure of gear and a reference circle used for calculation. It is a circle that can exist for a single gear. When a pair of gears are assembled according to the standard center distance, the total displacement coefficient becomes, and the pitch circle and indexing circle coincide. If it is the opposite, it will not coincide.
Indexing circle is a virtual circle whose end face is the product of module and number of teeth.
The synchronous belt pulley node is the focus formed by the common tangent of the two gear base circles and the connecting line between the center points of the two gears.
The pitch radius of synchronous belt pulley refers to the radius of nodes, which is called pitch radius.
The pitch diameter of synchronous belt pulley refers to the pitch diameter when the center distance of a pair of gears is fixed.
Therefore, there is no pitch diameter for a single gear. Nodes and pitch circles are formed only when two gears mesh. In standard gear transmission and high displacement gear transmission, the pitch circle and indexing circle are equal.
The pitch radius of the pinion can be equal to the number of teeth of the pinion compared with the number of teeth of the big gear, and then multiplied by the actual center distance. In the same way, we can get the pitch radius of the big gear. However, we should note that the pitch diameter is not necessarily equal to the number of teeth multiplied by the modulus.
The pitch diameter of synchronous belt pulley is a very important number, because it is related to the calculation of many data on the gear. For example, calculate the diameter of the dividing circle.
Dp=p × Z/π
The pitch diameter is DP, the number of teeth is Z, and the PI is π.
De= Dp-2 δ
The synchronous pulley has a pitch diameter of DP and a pitch top distance of δ， The diameter of the outer circle is de.
Dp=R × Z÷ZZ
The pitch radius is DP, the center distance is r, the number of teeth is Z, and the sum of the number of teeth is ZZ
