Times：2025/12/4
In automotive transmission systems and other systems, universal transmission devices must be used to achieve power transmission between shafts with intersecting axes or frequently changing relative positions. This article mainly introduces the classification of constant velocity universal joints in universal joints, the material selection of components, the processing technology of constant velocity universal joint components, and how to choose tool materials to process constant velocity universal joint components.
At present, the commonly used constant velocity universal joint in cars is the ball cage universal joint. The function of the ball cage universal joint is to transmit the power of the engine from the transmission to the two front wheels, driving the car to travel at high speed. It mainly consists of spherical shell, star shaped sleeve, retaining frame, steel ball and other main components. Due to the heavy driving torque transmitted by the constant velocity universal joint, it has high transmission accuracy with heavy loads, high demand, and is a safety component. Therefore, its main parts are made of precision forgings.
The classification of constant velocity universal joints is divided into fixed type and telescopic type according to their working performance. According to the installation type and shape in automobiles, it can be divided into end closed type, axle sleeve type, flange type, and disc type. The total components of the constant velocity universal joint transmission shaft are front wheel drive and rear wheel drive. The following figure shows a fixed cage type constant velocity universal joint.
3、 The materials of the main components of the constant velocity universal joint and the key factors determining its quality
(1) The material of the main components of the constant velocity universal joint: The commonly used material for the spherical shell is 55 # steel. The characteristics of 55 # steel are good rigidity, high strength, and wear resistance. Star shaped sleeve, commonly used material for retaining frame is 20CrMoTi. Characteristics of 20CrMoTi: After carburizing, the steel grains are refined and uniform, with good surface tensile and bending fatigue strength. The heart has sufficient strength and toughness, which improves wear resistance. The commonly used material for steel balls is GCr15.
(2) The key to determining the quality of constant velocity universal joint components
In order to ensure that the ball cage universal joint rotates flexibly, without looseness or abnormal noise after assembly, and to ensure assembly with the entire vehicle. The main key factors determining the quality of constant velocity universal joint components during processing are: (1) strict control of the tolerance requirements for the distance between the three pairs of ball paths and two steel balls in the spherical shell and star sleeve; (2) It is necessary to strictly control the tolerance requirements for the six equal parts of the spherical shell''s six lanes and the star shaped sleeve''s six lanes; (3) The tolerance requirements for the eccentricity between the center height of the spherical surface inside the spherical shell and the center height of the raceway, as well as the center height of the outer spherical surface of the star shaped sleeve and the center height of the raceway, must be strictly controlled; (4) Strictly control the coaxiality of the spherical surface inside the spherical shell and the six lanes, and the coaxiality tolerance requirements of the outer spherical surface of the star shaped sleeve and the six lanes; (5) It must meet the assembly requirements of the original vehicle model for spherical shell bolts, external splines, and their total length, as well as the fit requirements between the star shaped internal splines and the core shaft.
Quality requirements and processing technology for controlling the main components in the processing of constant velocity universal joints:
(1) As a component that drives high-speed driving of cars, constant velocity universal joints require high precision and strict coordination between each other. So, the quality issues that must be guaranteed when processing constant velocity universal joint components are: (1) Quality requirements for spherical shells: commonly used material 55 # steel, the hardness of the spline thread after heat treatment (high-frequency quenching) should reach HRC52-58, the hardness of the raceway after heat treatment should reach HRC52-58, and the dimensional accuracy and form error should meet the requirements of the drawing. No cracks detected during the inspection. (2) Quality requirements for star shaped sleeves and retaining frames: commonly used material 20CrMoTi, heat treatment using carburizing quenching, hardness reaching HRC58-62, dimensional accuracy and form error must meet the requirements of the drawings. No cracks detected during the inspection.
(2) The main components of the constant velocity universal joint are generally purchased parts, and subsequent processes such as turning, milling, rubbing, and grinding are independently processed. Design the machining process based on the quality requirements for the constant velocity universal joint components mentioned above.
1) The processing technology of spherical shells: forging (purchased parts) - rough turning (outer circle, inner hole) - fine turning (outer circle, inner hole) - milling six raceways - rubbing spline threads - heat treatment - grinding outer circle, end face - grinding inner hole, six raceways - flaw detection - cleaning.
2) The processing technology of star shaped sleeve: inner circular end face, outer circular end face - flower key - milling six ball paths - heat treatment - grinding outer circular surface - grinding six ball paths.
3) Maintain the machining process: inner circular end face - outer circular end face - punching window hole - milling window hole - heat treatment - grinding outer circular surface, inner circular surface - grinding six window holes
After heat treatment, all components meet the quality requirements of the constant velocity universal joint. In order to ensure the accuracy required by the drawing, grinding is often used for the main components after heat treatment. However, constant velocity universal joint components are generally mass-produced, and the use of grinding methods affects processing efficiency.
How to process constant velocity universal joint components after heat treatment
More and more processing plants are mass producing universal joints, which cannot meet the processing needs by using grinding methods. With the emergence of new technologies and processes in the cutting tool industry, the "car instead of grinding" process has emerged, replacing grinding machines with lathes and grinding wheels with blades, greatly improving processing efficiency.
At present, the tool materials for processing constant velocity universal joint components include hard alloy tools, ceramic tools, and cubic boron nitride tools. The use of hard alloy cutting tools to process constant velocity universal joint components often results in wear resistance, while the use of ceramic cutting tools to process constant velocity universal joint components is prone to tool breakage when encountering interruptions; Cubic boron nitride cutting tools are currently the most suitable tools for processing quenched steel parts. Among them, the cubic boron nitride cutting tools BN-H10 and BN-H20 developed in China can effectively precision machine outer ball cage surface parts. Not only is the tool life long, but the cost is also lower compared to foreign PCBN cutting tools.