advantage

shortcoming

Plane gear mechanism

space gear mechanism

When the straight line L performs pure rolling along a circle, the trajectory AK of any point K on the straight line is called the involute of the circle.

The length of BK on the occurrence line is equal to the arc length rolled over

The occurrence line is both the normal to the involute and the tangent to the base circle

The angle between the normal BK (pressure direction line) and the velocity vK direction of point K is called the pressure angle of the involute tooth profile at point K

The shape of the involute depends on the size of the base circle. The larger the base circle, the straighter the involute. As the radius of the base circle approaches infinity, the involute approaches a straight line.

There are no involutes within the base circle

Number of teeth: z

Base circle: db, rb

Addendum circle: da, ra

Root circle: df, rf

Graduation circle pressure angle: α

Top height coefficient: h*a, ha = h*a m

Head clearance coefficient: c*, hf = ( h*a c*) m

The indexing circle module and pressure angle are standard values.

With standard addendum and root heights

The thickness of the indexing circular tooth is equal to the width of the tooth space

A pair of involute gears have two pairs of teeth participating in meshing at the same time. The working side of the two gear teeth The meshing points of the tooth profile are K and K' respectively. In order to ensure a constant transmission ratio, the two meshing points K and K' must fall on the meshing line N1N2 at the same time.

The gap between tooth profiles is called flank clearance

The measurement of tooth side clearance is called pitch circle tooth side clearance, which is the difference between the tooth space width on one wheel's pitch circle and the other The difference in tooth thickness on the pitch circle

The existence of tooth side clearance will produce impact between teeth and affect the stability of gear transmission. Therefore, this gap can only be very small and is usually guaranteed by the gear tolerance. The gear motion design is still designed with no backlash

When entering mesh, the tooth root part of the driving wheel must be in contact with the tooth top of the driven wheel. When meshing is completed, the tooth tip of the driving wheel must be partially in contact with the tooth root of the driven wheel.

Continuous fixed transmission ratio transmission conditions: on the meshing line, the previous pair of tooth profiles terminates meshing The front and rear pair of tooth profiles have entered into mesh, that is, there must be at least one on the meshing line at any time. A pair of tooth profiles are in meshing state

Define the degree of coincidence: =AE/EK=AE/Pb

Disc milling cutter

Finger milling cutter

Gear inserting knife

Rack inserter

gear hob