Application, Tightening Mode And Parameter Selection Of Torque Tightening Machine

A complete engine assembly consists of thousands of different parts and components. The major task for assembling engine is to assemble these parts and components together based on the requirement. During the assembling procedure, the most common assembling operation is to tighten the bolts. That is to say, tightening the bolts is penetrated in the whole assembling procedure. From another point of view, if the bolts are assembled very well, that is mainly decided by the tightening torque, the assembling process will be accessed to success. The control accuracy of tightening torque is normally used to judge the assembling quality of engine in the world,so it is very important to improve the control accuracy of tighten torque. At present, one of the most effective methods to assure tightening accuracy is to apply the combined torque tightening machine.Torque tightening machine has been applied widely in various fields of society. Torque tightening machine has been developing continuously in order to meet the requirement of different kinds of bolts and various tightening methods and meet the higher expectation of the user. The tightening machine with higher quality and operating performance has been developing continuously based on the latest tightening technique. The main characteristics of tightening machine are: miniature, less weight, higher speed digital processor, easier to maintenance, superior operational interface, more completed function and overall data communication modes. A lot of different tightening methods have been applied in the latest tightening technique in order to meet all kinds of tightening demands, such as inner torque/angle, torque/angle surveillance, false image angle, yielding etc.. Furthermore, the tightening changing rate and space interval can also be monitored, which are used to check the abnormal tightening. All these functions can guarantee the tightening accuracy.This paper is divided into four parts, which includes the application of torque tightening machine, tightening modes and parameters selection.The application of torque tightening machine is introduced in the first part, which mainly includes the definition of torque tightening machine, the current situation of torque tightening machine, the feasibility of automobile application, the structure and working theory, the advantage and characteristic of torque tightening machine. The different tightening method is also briefly introduced in the first part.The basic knowledge of thread connection is discussed in the second part, which includes the types of thread connection, force analysis, relationship of clamping force and tightening torque, major parameters of tightening, relationship of clamping force and deformation amount. After the above discussing, the following conclusions are drawn: I. Clamping force and tightening force are two completely different concepts;II. It is not acceptable to control the clamping force by increasing and decreasing of tightening torque merely. III. The key points is to analyze the tightening factors correctly;IV. The key factor which effects the clamping force is deformation amount of bolts;V. The correct tightening process is gotten.The current tightening methods will be analyzed and expatiated one by one in the third part based on the conclusion of second part. The current tightening methods include torque control method, torque-angle control and yielding point control etc. The tools and equipments used in the above methods will also be introduced in this part. The checking methods about how to evaluate the tightening quality and effect will be introduced in the part finally.The tightening problems found during the developing and small batch producing phase of DA5 engine and the solving methods will be introduced in the forth part.The Initial tightening parameter of the connecting rod is 15Nm+40°. The"clank"noise appears on engine at trial running. 1320 groups of data are collected and analyzed. The final tightening parameter is set to be 20Nm+37o after using interchanging and measuring technique. The tightening defaults have never been found during the long time trial and patch production. The problems are solved completely.Based on the same kind of method, 440 groups of data are collected, the alarming limitation of tightening machine for crack shaft case(namely torque supervising value ) is changed from 47.0 Nm～64.0 Nm to 50.9 Nm～67.7 Nm. . The limitation of converse disassembling(namely manual measuring torque) is 53 Nm～74 Nm. All these parameters have been verified. These problems are solved completely.The initial tightening parameter of cylinder head bolts is set 40Nm+120o. The"clank"noise appears on engine at trial running. After collecting 240 groups of data for the fore and after cylinder head and analyzing, the multi-step tightening process is used. The steps are as the following: 1st step: 20 Nm(15rpm), 2nd step: 40 Nm(8rpm), 3rd step: rotating 60o(8rpm), 4th step: rotating 60o(8rpm) again. Attenuation problem has been overcome by the verification.This subject is bases on my working experience on the first set of torque tightening machine in our factory. With the examples of tightening bolts for connecting rod, crankshaft case of cylinder block and cylinder head during the research and manufacture of DA5 and after performance contrasting between domestic and importing parts, the connection and tightening of thread, torque tightening machine function, torque tightening machine application, tightening mode of torque tightening machine and verification of tightening parameters are discussed in the subject. The conclusion of research would be helpful for the people to select the correct tightening mode, verify the tightening parameters and do the trouble shooting.