Views: 1 Author: Site Editor Publish Time: 2021-11-29 Origin: Site
A single universal cross joint is a kind of unequal speed universal joint. Its characteristic is that when there is an Angle between the driving shaft and the driven shaft, the equal speed transmission can not be carried out, so that the angular velocity of the driving shaft and the driven shaft are not equal periodically. However, the design scheme of rational double cross joint transmission can achieve equal speed transmission. The universal joint where the angular velocity of the main and driven axes is still equal when the included Angle between the two axes changes is called the constant angular velocity universal joint or constant velocity universal joint; Quasi-constant velocity universal joint is a kind of approximate constant velocity universal joint, which can realize the approximate constant velocity transmission between the main shaft and the driven shaft through the indexing mechanism and other parts.
The common cross shaft universal joint is generally composed of two universal joint forks and the cross shaft, needle roller bearings and their axial positioning parts and oil seals connected with them. The cross shaft journal is fitted in the hole of the universal joint fork by means of a needle roller bearing. In order to prevent axial movement of needle roller bearings, bearing axial positioning measures should be taken in structural design. At present, the common axial positioning methods of needle roller bearings include cover plate, clamp ring type, plastic ring positioning type and tile cover fixed type.
In the axial positioning mode of ordinary cover plate bearing, bolts and cover plates are generally used to fix the sleeve on the universal joint fork, and the bolt is locked with a locking plate. The advantage of this way is reliable work, convenient disassembly, but the number of parts more. Using elastic plate structure scheme is to elastic plate spot welding on the bottom of the bearing seat, after the assembly, the elastic plate on the bottom of the bearing has a certain pressure, so as to avoid high speed rotates due to centrifugal force role, at the shaft end face with a gap between the bottom of the bearing seat and cause cross shaft axial channeling, which can avoid because of this dynamic shaft dynamic balance of damage.
The clasp type has the advantages of simple structure, reliable operation, few parts and small quality, and can be divided into two types of external card type and internal card type. The plastic ring positioning structure is to open an annular groove in the middle of the bearing hole of the outer circle of the bearing bowl and universal joint fork. When the needle roller bearing dynamic fit is loaded into the universal joint fork to the correct position, the plastic is pressed into the ring groove through the small hole on the universal joint fork. When the plastic is spilled out of the hole perpendicular to the ring groove on the universal joint fork, it indicates that the plastic has been filled with the ring groove. This structure has reliable axial positioning and small axial movement of the cross shaft, but it is not convenient to disassemble and assemble.
In order to prevent the axial movement and heating of the cross shaft, ensure that the end clearance of the cross shaft is always zero under any working condition, some structures are installed between the end of the cross shaft and the bearing bowl with end thrust needle or roller bearings.
The universal joint bears large torque and alternating load in the work, its main damage form is the wear of cross shaft journal and needle roller bearing, the indentation and spalling of cross shaft journal and needle roller bearing bowl working surface. It is generally considered that when wear or indentation exceeds 0.25mm, the cross universal joint must be scrapped and replaced. In order to improve its service life, commonly include combined lubrication seal requirements. A variety of designs are included to lubricate and protect cross journal and needle roller bearings.
Traditional felt oil seal due to oil leakage, poor dustproof and waterproof effect, lubricating oil filling, air blockage may occur in individual needle roller bearings and cause oil shortage, has been unable to meet the higher and higher. Cars are often sealed with grease during assembly to reduce the lubrication point of the vehicle, and the use of double-edged or multi-edged rubber oil seal with better sealing effect.