Role of mechanical transmission: The role of mechanical transmission is to transmit motion and force. The types of commonly used mechanical transmission systems include gear transmission, worm gear transmission, belt transmission, chain transmission, gear train, etc.
Gear transmission: gear transmission is realized by shifting the driven gear by the driving gear in turn. One of its basic requirements is that the ratio of its instantaneous angular velocity must remain unchanged.
Classification of gear transmission: there are many types of gear transmission. According to the relative motion of two gears, it can be divided into plane gear transmission and space gear transmission. The initial contact of spur gear teeth is a line extending across the entire tooth surface. The initial contact of helical gear teeth is a point. When the teeth enter more meshing, it becomes a line. In spur gears, the contact is parallel to the axis of rotation. In helical gears, the line is diagonal across the tooth surface. It is the gradual meshing of gears and the smooth transmission of motion from one tooth to another, which makes the helical gears have the ability of smooth transmission of motion under high speed and heavy load. The helical gear makes the bearing of the shaft bear radial and axial forces.
When the axial force becomes larger or has some effect due to other reasons, it can make herringbone gear. Double helical gear (herringbone gear) is equivalent to two helical gears installed on the same shaft side by side in reverse direction. They produce opposite axial thrust action, thus eliminating the axial thrust. When two or more one-way helical gears are on the same shaft, the tooth direction of the gear shall be selected to generate the minimum axial thrust.
Worm gear and worm drive: Worm gear and worm drive is used to transfer the motion and power between two shafts whose space is perpendicular to each other but not intersected. The turbine is similar to the staggered helical gear. Pinions, namely worms, have a small number of teeth, usually one to four teeth. Because they are completely wrapped on the pitch cylinder, they are called threaded teeth.
The matching gear is called a turbine, which is not a real gear. Worm and turbine are usually used to provide large angular speed reduction ratio for transmission between vertical intersecting shafts. The turbine is not a helical gear, so its tooth top surface is made into a concave shape to adapt to the curvature of the worm, in order to form first contact rather than point contact. However, the worm turbine transmission mechanism has the disadvantage of large sliding speed between teeth, just like the staggered helical gear.
Belt drive: belt drive transmits motion and power through intermediate flexible parts (belts). Belt drive is mainly used in situations where two shafts are parallel and the rotation direction is the same. This drive is called open drive.
Chain drive: The chain drive is composed of the main and driven sprockets installed on the parallel shaft and the circular chain wound on the sprocket. The chain is used as the intermediate flexible part, and the motion and power are transmitted by the meshing of the chain and sprocket teeth. Compared with belt drive, chain drive has the following main features: no elastic sliding and slipping, and can maintain accurate transmission ratio; The required tension is small, and the pressure acting on the shaft is also small; Compact structure; It can work under harsh environmental conditions such as high temperature and oil pollution.
Compared with gear drive, chain drive has the following main characteristics: low requirements for manufacturing and installation accuracy; When the center distance is large, its transmission structure is simple; The instantaneous chain speed and instantaneous transmission ratio are not constant, and the transmission stability is poor.
Source: Network
