Gear Classification
Gears can be divided into three categories: cylindrical gears, bevel gears, and worm gears and worm wheels.
1. Types and characteristics of cylindrical gears
Cylindrical spur gears
The axes of the large and small gears are parallel to each other; the length of the gear teeth is parallel to the gear axis; when the external gears mesh, the two gears rotate in opposite directions; when the internal gears mesh, the two gears rotate in the same direction; the tooth profile can be made into normal teeth, short teeth, and can be modified.
Cylindrical helical gears
The axes of the large and small gears are parallel to each other; in external meshing transmission, the two gears rotate in opposite directions; in internal meshing transmission, the two gears rotate in the same direction; the tooth profile can be made into normal teeth or short teeth, and can be modified; the tooth length line of the gear is inclined at an angle to the gear axis; the meshing transmission is smoother than that of spur gear transmission and transmits greater force.
helical gear
The axes of the large and small gears can be parallel, intersecting, or perpendicular to each other in space; the rotation directions of the large and small gears can be the same or opposite; the helix angles of the large and small gears can be equal or unequal; when the helix angle of the small gear becomes large enough, it becomes a tadpole.
Gears and racks
The gear meshing with the rack can be a spur gear or a helical gear, and possesses the characteristics of either. Rack and gear transmission converts rotation into linear motion or motion into rotation. The rack is formed when the gear diameter is infinitely large.
2. Types and characteristics of bevel gears
Straight bevel gears
The axes of the large and small gears intersect at the apex of the cone; when the pitch cone angle of the large gear is equal to 90°, it becomes a planar bevel gear; when it is greater than 90°, it becomes an internal meshing bevel gear.
Helical bevel gears
The tooth line is oblique and tangent to a certain circle, and the tooth line does not intersect with the cone tip; the wrench angles of the large and small gears are equal and opposite in direction; the transmission is smoother than that of straight bevel gears.
Spiral bevel gears
Smooth transmission, high force transmission, suitable for high-speed transmission; the wreath angles of the large and small gears are equal and opposite in direction; the axes of the two gears intersect at the apex of the cone; spiral bevel gears are further divided into circular arc teeth, extended epicycloid teeth, and quasi-involute teeth.
3. Types and characteristics of worms and worm gears
Cylindrical worm and worm wheel
Archimedes worm gear
The tooth profile on the axial section of the worm is a straight line.
linear worm gear
The tooth profile on the normal tangent plane of the worm gear helix is a straight line.
Involute worm gear
The tooth profile on the plane parallel to the worm axis and tangent to the base cylinder is straight.
Circular arc worm and worm wheel
High efficiency, good oil film formation; large load-bearing capacity; complex manufacturing and assembly; also known as a spherical worm gear pair; the tooth profile is further divided into: original type and modified type. The purpose of modification is to facilitate the formation of an oil film in the worm gear during transmission.
Gear dimension parameter calculation formula chart
1. Calculation of parameters for internal gear module
2. Calculation of parameters for spur gears with modular actuation
3. Calculation of parameters for helical module gears
4. Calculation of parameters for modified module gears
5. Calculation of parameters for spur gears with diametral pitch.
6. Calculation of parameters for helical diaphragmatic gears
7. Calculation of rack parameters
Gear transmission
Gear transmissions are classified according to whether the axis position of each gear is fixed during transmission. Gear trains are divided into two basic types: planetary gear trains and fixed-axis gear trains.
Fixed-axis gear trains include planar fixed-axis gear trains and spatial fixed-axis gear trains, in which the geometric axis positions of all gears remain fixed during transmission.
Based on their different degrees of freedom, planetary gear trains can be further divided into planetary gear trains and differential gear trains. Planetary gear trains have one degree of freedom, while differential gear trains have two degrees of freedom.
