In automotive drive trains and other systems, in order to achieve power transmission between rotating shafts where the axes intersect or the relative position often changes, universal transmission must be used. This article mainly introduces the classification of constant velocity universal joints in universal joints, the material selection of parts, and the processing technology of constant velocity universal joint parts.
At present, the constant velocity universal joints commonly used on cars are ball cage universal joints. The function of the ball cage universal joint is to transfer the power of the engine from the transmission to the two front wheels to drive the car at high speed. It mainly consists of spherical shell, star sleeve, cage, steel ball and other main parts. Because the constant velocity universal joint transmits heavy driving torque, with the load being heavy, the transmission precision is high, the demand is large, and it is a safety part, so its main parts are processed by precision forging.
Classification of constant velocity universal joints: divided into fixed type and telescopic type according to working performance. According to the installation type and shape in the car, it is divided into closed end type, shaft sleeve type, flange type, and roulette type. The constant velocity universal joint drive shaft has two components: front-wheel drive and rear-wheel drive. The following picture shows a fixed ball cage constant velocity joint
Third, the material of the main parts of the constant velocity universal joint and the key to determine the quality
1) The material of the main parts of the constant velocity universal joint: The common material of the spherical shell is 55 # steel, 55 # steel. Features: good rigidity, high strength and wear resistance. Star sleeve, the common material of the cage is 20CrMoTi, 20CrMoTi Characteristics: After carburizing, the steel grains are refined, uniform, and have good surface tensile and bending fatigue strength. The heart has sufficient strength and toughness to improve wear resistance. The steel ball is usually made of GCr15.
2) The key to determining the quality of constant velocity universal joint parts
In order to ensure that the ball cage universal joint can rotate flexibly after assembly, no looseness, no abnormal noise, and ensure assembly with the vehicle. During the processing of constant velocity universal joint parts, the main key to determine the quality is: (1) the tolerance requirements of the distance between the spherical shell and the star-shaped three pairs of fairways and the two steel balls must be strictly controlled; (2) the sphericity must be strictly controlled Tolerance requirements for the six equal divisions of the six fairways of the shell and the six fairways of the star-shaped sleeve; (3) The tolerance of the eccentricity between the spherical center height of the spherical shell and the fairway center height and the outer diameter of the star-shaped sleeve and the fairway center height must be strictly controlled Requirements; (4) Strictly control the coaxiality of the spherical surface of the spherical shell and the six fairways, and the coaxiality tolerance requirements of the outer spherical surface of the star sleeve and the six fairways; (5) Must meet the original model's spherical shell bolts, external splines and The total length of the assembly requirements and the matching requirements of the spline inside the star sleeve and the mandrel.
Quality requirements and processing technology for controlling the main parts in constant velocity universal joints:
1) Constant velocity universal joints, as components that drive cars to travel at high speeds, require high precision and strict cooperation with each other. Therefore, the quality issues that must be guaranteed when processing constant velocity universal joint parts are: (1) Quality requirements for spherical shells: common material 55 # steel, the hardness of the spline thread parts after heat treatment (high frequency quenching) reaches HRC52- 58, the hardness of the raceway after heat treatment must reach HRC52-58, and the dimensional accuracy and shape and position error must meet the requirements of the drawing. No cracks were detected. (2) Quality requirements for star sleeves and cages: commonly used material 20CrMoTi, heat treatment using carburizing and quenching, hardness reaching HRC58-62, dimensional accuracy and form and position error must meet the requirements of the drawing. No cracks were detected.
2) The main parts and components in constant velocity universal joints are generally purchased parts, and subsequent processes such as turning, milling, rubbing, and grinding are processed independently. Processing technology designed according to the quality requirements of constant velocity universal joint parts.
1) Spherical shell processing technology: forgings (purchased parts)-rough turning (external circle, inner hole)-fine turning (external circle, inner hole)-milling six raceways-rubbing spline thread-heat treatment-grinding outer circle , End face-grinding inner hole, six fairways-flaw detection-cleaning.
2) Machining process of star sleeve: inner round end face, outer round end face—pulled spline—milled six fairways—heat treatment—grind outer round surface—milled six fairways.
3) Maintaining the processing technology: inner round end face of the car-outer round end face of the car-punching window hole-milling window hole-heat treatment-grinding the outer round surface, inner round surface-grinding six window holes
After the heat treatment, the parts meet the quality requirements of the constant velocity universal joint. The main parts are often heat-treated to ensure the accuracy of the drawings. However, constant velocity universal joint parts generally belong to mass production, and the grinding method is used to affect the processing efficiency.
How to process constant velocity joint parts after heat treatment
More and more processing plants produce universal joints in batches, adopting grinding methods to meet processing requirements, and as the new technology and new technology of the tool industry are not innovated, the "car-based grinding" process has appeared, and lathes have been used. The process of replacing the grinding machine and the blade instead of the grinding wheel greatly improves the processing efficiency.
At present, the cutting tool materials for processing constant velocity universal joint parts include hard alloy cutting tools, ceramic cutting tools and cubic boron nitride cutting tools. Constant-speed universal joint parts processed with cemented carbide tools often do not wear out, and constant-speed universal joint parts processed with ceramic tools are prone to collapse when interrupted; cubic boron nitride tools are currently the most suitable For cutting hardened steel parts, the cubic boron nitride cutting tools BN-H10 and BN-H20 developed by our country can effectively finish the outer ball cage parts, which not only has a long tool life, but also has a relatively low cost compared to foreign PCBN tools.
