What is the difference between involute gears and cycloidal gears?
The difference between cycloidal profile and involute profile
Although comparing these two tooth profiles, there is one thing I hope everyone can pay attention to: involute gears are just a special case of cycloidal gears.
(1) The pressure angle of the cycloidal profile is maximum at the beginning of meshing, decreases to zero at the tooth node, and increases again to its maximum value at the end of meshing, resulting in abnormal gear operation. In the involute profile, the pressure angle remains constant throughout the entire meshing period, which leads to smooth operation of the gear.
(2) The teeth of the cycloid profile are hyperbolic, consisting of epitrochoids and hypocycloids. This makes the manufacturing of such gears very difficult. The teeth of the involute profile are "single curves", making them easy to manufacture.
Involute tooth profile
Cycloidal profile
(3) Cycloid gears are complex to manufacture and have higher costs, while involute gears are simple to manufacture and therefore cheaper in price. We all know that the tooth profile of the involute gear cutter is straight.
(4) Cycloid gear teeth require precise center distance to transmit a constant speed ratio. But small changes in the center distance of involute gear teeth will not affect the speed ratio.
(5) Due to the presence of a root like shape near the cycloidal gear tooth surface, there will be no interference. But the involute gear teeth will interfere, and the root of the involute gear will undergo nonlinear changes.
(6) Cycloid gear teeth have extended tooth surfaces, resulting in higher strength. And involute gear teeth have radial tooth surfaces, which have lower strength compared to cycloidal gear teeth.
(7) The convex surface of cycloidal gear teeth always contacts the concave surface, resulting in less wear. However, the involute gear teeth have two convex surfaces in contact, resulting in significant wear.
Take a look at what was mentioned earlier:
Cycloidal gear tooth profile
Involute gear tooth profile
Mathematically speaking, a cycloid is the trajectory of a point on a circumference that rolls on a straight line without sliding.
Mathematically speaking, an involute is the trajectory of a point on a straight line that rolls on a circumference without sliding.
The tooth profile of cycloidal gears is hyperbolic, and the tooth profiles of both epitrochoids and hypocycloids are hyperbolic, which makes the manufacturing process very complicated.
The involute gear profile involves a single curve of teeth, making it easy to manufacture.
During the entire meshing process, the pressure angle changes from its maximum value to zero, and then increases again to its maximum value, resulting in unstable gear operation.
The pressure angle remains constant throughout the entire meshing process of the gear teeth. This enables the gears to operate smoothly.
The manufacturing cost of cycloidal gears is relatively high
The manufacturing cost is quite low
The center distance must be precise in order to transmit a constant speed ratio
The center distance allows for variation as it does not affect the speed ratio
No root cutting phenomenon will occur
If the minimum number of teeth condition on the gear is not followed, root cutting will occur
