The cross-shaft universal coupling is a kind of movable rigid coupling. It has a larger axis inclination, which can generally be in the range of 5°～25°. It can realize that the two shafts are not on the same axis. It is connected, and the inclination of the axis between the two shafts and the wide range of axial expansion and contraction can be changed at any time during the rotation.In addition, due to the unique characteristics of this type of coupling, double-headed universal joints must be used and certain layout conditions must be met, otherwise unequal speeds will occur.

1. Product Overview

　　The cross-shaft universal coupling is a universal transmission base. Its main feature is that it can connect two transmission shafts that are not on the same axis, and can reliably transmit torque and motion.The coupling has the advantages of high carrying capacity, long service life, smooth operation, no noise, large axial compensation, and simple maintenance.Mainly used for steel rolling machinery, lifting and transporting machinery, petroleum drilling machinery, engineering and mining machinery, ships and other heavy machinery.

　　The cross shaft universal joint is mainly composed of two single-head universal joints and spline pairs.The single-head universal joint consists of two fork heads, a cross pin shaft and multiple rows of short cylindrical roller bearings.During the operation of the single-head universal joint, the active end fork drives a symmetrical trunnion of the cross pin shaft and drives the driven end fork head to run together through the other symmetrical trunnion of the cross pin shaft, while the trunnion of the cross pin shaft There are multiple rows of short cylindrical roller bearings installed between the fork head holes to form rolling friction, so it has a high load-bearing capacity and flexible swing.

　　The cross shaft universal coupling is divided into four structural types according to the fixing method of the bearing and the shape of the fork head: namely, split bearing seat cross shaft universal coupling (referred to as SWP type), integral bearing seat cross shaft Type universal coupling (SWZ type for short), integral fork cross shaft universal coupling (SWC type for short) and half fork cross shaft universal coupling (SWB type for short).In addition, in order to meet the needs of high-speed wire and bar rolling mills, there is also a large telescopic cross universal coupling.The current SWP, SWZ and SWC cross-shaft universal joints have respectively formulated industry standards and formed specialized production.

　　Due to the existence of unequal speed and angular acceleration at the driven end of the single-head universal joint, it is not suitable for high-speed and heavy-duty. In order to eliminate this drawback, generally double-head universal joints are used.At the same time, the following three conditions should be met in the arrangement of the universal coupling: 1 the inclination angle between the intermediate shaft and the driving shaft should be equal to the inclination angle between the intermediate shaft and the driven shaft; 2 the forks at both ends of the intermediate shaft must be located Same phase; 3 The center line between the main and driven shafts and the intermediate shaft must be in the same plane.

　　The cross-shaft universal joint has the following advantages in addition to high load carrying capacity, large allowable axis inclination, large expansion and long service life, and the following advantages: 1. The rotation is based on rolling contact bearings, with low power loss and high transmission efficiency. 98.8%～99.8%, which can reduce power consumption by 5%～15%; 2 In the case of the same rotating diameter, it can transmit greater torque than other couplings; 3 smooth operation, no vibration, impact resistance, more suitable In the positive and negative direction; 4 good lubrication conditions, no oil leakage, simple maintenance, low maintenance and repair costs; 5 noise can be reduced by 15 to 30 decibels, to protect the physical and mental health of the operators.

2. Product technical level and status quo

　　my country has formulated three standards for cross shaft universal couplings: JB 3241-91 "SWP split bearing seat cross shaft universal coupling", JB/T 3242-93 "SWZ type integral bearing seat" Cross Shaft Universal Coupling" and JB 5513-91 "SWC Type Integral Fork Cross Shaft Universal Coupling", which are currently the three types of crosses with the widest application range and the largest amount at home and abroad Shaft universal coupling.For example, GWB and Voith in Germany produce SWP and SWC respectively, ПAJico from Koyo in Japan produces SWZ and SWP respectively, while the United States and Italy produce SWB, SWZ and SWP.From the three standards formulated by our country, whether it is the performance parameters of the coupling or the mechanical properties of the main parts of the material, heat treatment, dimensional deviation, form and position tolerance, roughness and other technical requirements have been specified, and the technical level has reached The level of similar products in advanced foreign countries.The main technical indicators stipulated by the standard are: the rotating diameter is φ100～φ1200mm, the transferable torque is 2.5～9000kN.m, the axis inclination is 5°～25°, and the telescopic amount is 1000mm.

　　The quality of the key components of the cross pin shaft, rolling bearing and spline pair in the cross shaft universal coupling will directly affect the load carrying capacity and service life of the coupling.Through years of production practice, continuous improvement of materials, heat treatment, processing technology and other aspects have basically met the requirements of the standard, and to a certain extent also met the needs of the market.

3. Development trends at home and abroad

　　Cross-shaft universal coupling, from the development trend at home and abroad, on the one hand, how to improve its load-bearing capacity and quality, and prolong its service life; on the other hand, how to expand its application range to meet a variety of mechanical equipment Needs.To this end, in addition to appropriate improvements to the structure, connection methods, etc., higher requirements should also be put forward for its main components.

Design: In the new design, finite element analysis will be used for structure, stress, deformation, etc., and optimized design will be carried out to make the design more advanced and reasonable.

Cross pin shaft: The cross pin shaft is one of the key parts of the cross shaft universal coupling, which will directly affect the carrying capacity and service life.Therefore, from material selection, blank, heat treatment to processing and testing, more advanced techniques and methods will be adopted to meet the design requirements.From the perspective of development, it is more reasonable that the material of the cross pin should be changed to low-carbon chromium-nickel steel or low-carbon chromium-nickel-molybdenum steel.The heat treatment should use an automatically controlled carburizing furnace to facilitate strict control of surface hardness, carburized layer depth and deformation.In terms of processing, it will consider how to improve the processing accuracy and production efficiency of parts, and adopt advanced process equipment, such as CNC machine tools.

Bearing: The bearing in the cross shaft universal joint is also one of the key parts, and it has the same importance as the cross pin shaft. It is a combined bearing composed of multiple rows of short cylindrical roller bearings and thrust bearings.Because the bearing is relatively special and requires a certain amount of interference between the inner and outer diameters during assembly, it brings great difficulty to assembly and maintenance.In order to facilitate the disassembly and assembly, we should consider changing the structure of the bearing and carry out a new design to meet the new requirements.In addition, in order to increase the diameter of the cross pin shaft and meet the needs of large torque, the relationship between the roller diameter and the number of rollers of the bearing should be adjusted accordingly, and the method of reducing the diameter of the roller and increasing the number of rollers should be adopted to solve the problem. .The shape of the roller should also be changed appropriately, using a waist drum shape with a certain degree of convexity to reduce the boundary stress value of the roller.

Spline pair: The spline used in the cross-shaft universal coupling has two types: rectangular spline and involute spline, and the use of involute spline is more common.As the torque transmitted by the cross-shaft universal coupling is increasing and the operating speed is getting higher and higher, the requirements for the spline pair will be higher.On the one hand, the strength of the spline pair should be considered, and further research should be made from the tooth profile, heat treatment, and surface hardness. On the other hand, it is necessary to consider the smoothness of operation, improve the processing accuracy, and develop new processing techniques and methods.

4. Production and sales status and market forecast

　　Cross-shaft universal couplings have a broad market, and the annual demand is very large.According to the analysis of the current situation, the annual sales volume is about 30 million yuan, excluding imports.Due to the unstable quality of domestic products, the main drive shaft in some large-scale equipment could not meet the requirements for a while, so a part of the market was lost.Although this part of the market accounts for a small amount, the output value is indeed very high, accounting for about XNUMX% of the total sales.In order to reduce imports and expand exports, and increase annual sales, it is necessary to continuously improve existing products, improve their technical level and product quality, and maximize the market share.