The "art of the bite" in the mechanical world: getting to know the different types of gears
In the machinery industry, gear transmission is one of the most basic forms of transmission. Gear transmission structure is simple, high transmission efficiency, and can ensure accurate transmission ratio, so it is widely used in a variety of mechanical equipment.
The efficiency of gears is the transmission efficiency of gears under normal assembly conditions. If there is an incorrect installation, especially if the bevel gear is assembled at an incorrect distance resulting in an error in the conical intersection, the efficiency will be significantly reduced.
Parallel shaft gears
1. Spur gears: Cylindrical gears whose tooth lines are parallel to the centre line of the shaft.They are most widely used in power transmission because they are easy to process.
2. Helical gears: Cylindrical gears with helical tooth lines. They are widely used because they are stronger than spur gears and run smoothly. Axial thrust is generated during transmission.
3. Racks: A linear rack-like gear that meshes with a spur gear. It can be regarded as a special case when the pitch circle diameter of the spur gear becomes infinite.
4. Helical racks: A strip gear that meshes with a helical gear. This is equivalent to the case when the pitch diameter of the helical gear becomes infinite.
5. Internal gears: Gears that mesh with spur gears and have teeth machined on the inside of the ring. Mainly used in applications such as planetary gear drives and gear couplings.
6. Herringbone gears: A gear made by combining two helical gears with left and right-handed tooth lines. It has the advantage of not generating thrust in the axial direction.
Intersecting shaft gears
1. Miter gears: A curved tooth bevel gear with a helix angle of zero degrees.Because of the characteristics of both straight and curved bevel gears, the force on the tooth surface is the same as that of straight bevel gears.
2. Straight bevel gears: A bevel gear whose tooth line coincides with the bus of the pitch cone line. Since bevel gears are relatively easy to manufacture, they are used in a wide range of applications as transmission bevel gears.
3. Spiral bevel gears: Bevel gears with curved tooth lines and helical angles. Although it is more difficult to manufacture than straight bevel gears, it is widely used as a high-strength, low-noise gear.
Staggered shaft gears
1. Cylindrical Worm Gear: Cylindrical worm gear is a general term for a cylindrical worm gear and the worm wheel that meshes with it. The biggest feature is that it runs calmly and a large transmission ratio can be obtained with a single pair, but it has the disadvantage of low efficiency.
2. Staggered shaft helical gears: The name given to cylindrical worm gears when driven between staggered shafts. It can be used in the case of helical gears or helical gears and spur gears. The operation is smooth, but it is suitable for use only with light loads.
Gear material
The gear tooth body should have high resistance to fracture, tooth surface should have strong resistance to pitting, wear and high resistance to gluing, that is, the requirements: tooth surface hard, core tough. The gear material of Hezhong Heavy Industry often choose 20CrMnTi.
Among them, in the structural steel and tool steel, chromium (Cr) can significantly improve the strength, hardness and abrasion resistance, while reducing the Plasticity and toughness of steel. Chromium also improves the oxidation and corrosion resistance of steel, and is therefore an important alloying element for stainless steel and heat-resistant steel.
Manganese (Mn) is originally a weak deoxidiser. The appropriate amount of manganese can effectively improve the strength of steel, eliminate the sulfur, oxygen on the steel of the hot brittle effect, improve the hot working properties of steel, and improve the cold brittle tendency of steel, while not significantly reduce the plasticity of steel, impact toughness.
Titanium (Ti) is a strong deoxidiser in steel. It can make the internal organisation of steel dense, refine the grain force, reduce the aging sensitivity and cold brittleness of steel, while improving the welding performance.
Therefore, 20CrMnTi is often used to manufacture gears with high strength, high hardness and good toughness.
Machining of gears
The machining process of gears usually involves a series of steps: forging of tooth blanks, flat drilling of centre holes, fine turning of tooth blanks, hobbing, interpolation, shaving, grinding, spline rolling and straightening. Additional steps such as heat treatment (e.g. carburising and hardening) and cleaning are often involved to ensure that the quality of the product meets the requirements of the particular application.
In summary, the advantages of gears include operational reliability, high transmission efficiency, compact structure, etc., but there are also disadvantages such as high manufacturing costs, high precision requirements, and unsuitable for long-distance transmission. Choosing the right type of gear can optimise the performance of the machinery, but it is also necessary to make decisions based on specific application requirements and conditions.