Pre-tightening control of precision machine tool spindle bearings Guo Ming, Chen Zongnong, Wang Qingjiu Institute of Mechanical Design, Zhejiang University, Hangzhou 310027, China. Indeed 1; the machine's most preloaded force, its control, ç² and control of the mustard method. ancient. The feasibility of real-time control of preload is verified by the 1.1 Saki Moss Spring 乇 main system.
1 Introduction Precision machine tool spindles are usually supported by rolling bearings to ensure the spindle system has superior rotational accuracy, stiffness and thermal characteristics. Preloading technology must be employed. The traditional pre-tightening, including the pressure pre-tightening and positioning pre-tightening, enables the system to maintain a predetermined pre-tightening force or pre-tightening displacement, which cannot optimize the pre-tightening force for different working conditions. On-line control of the preload of the spindle bearings enables optimization of the preload condition.
Regarding the control of preload, domestic and foreign scholars have conducted a lot of theoretical and experimental research. According to the control principle, there are roughly two types of non-real-time control. It is realized by changing the structure of the bearing and adopting the principle of pre-compensation compensation. For example, the company's pre-tightening fund-funded technology attack, 857 only 03151 Guo Ming 1968, male, Nantong, Jiangsu, lecturer, doctoral student, engaged in textile machinery and automation of precision machine tool spindle system; Chen Zongnong 1948, male, Shaoxing, Zhejiang, professor, engaged in textile machinery and automation of precision machine tool spindle system宄; Wang Qingjiu 1969, female, Jiangsu Jiangyin man-made device with the help of oil chamber pressure to adjust, the tightening force size 2, but it is only adjustable, no pre-tightening force measurement, so it is non-real-time online. In addition, the pre-tightening control system developed by Keio University in Japan uses the deformation component on the bearing seat to measure the pre-tightening force under the working condition of the bearing, and the pre-tightening force is controlled by the compression element; the pre-tightening of the development of Harbin Institute of Technology The force 4 is determined by the characteristics of the piezoelectric crystal, and its deformation per 10,000 volt is 1. It is the total length of the piezoelectric crystal, and thus requires a high voltage.
Domestic and foreign scholars have also carried out a lot of theoretical analysis on the pre-tightening force of the bearing, but because the optimal pre-tightening force of the spindle bearing of the machine tool is related to various factors such as the bearing speed and temperature rise load, the spindle deformation bearing life lubrication condition, etc., it is necessary to determine the bearing The best pre-tightening force is that there is a large number of secondary mothers who are involved in the division.
To this end, this paper takes the 1000-type precision grinding machine spindle system as the object, and studies the load-bearing bearing 15 as the load cell, and the pre-tightening force control is the control method of the actuator. By using this method, the pre-tightening force of the machine shaft bearing can be realized.
Engineer, engaged in textile machinery and automation research.
2About the optimal pre-tightening force can automatically adjust the optimal pre-tightening force, and realize the automatic tracking correction of the pre-tightening force. From the theoretical analysis, the optimal pre-tightening force is a function of the rotational speed and the external load for a specific machine tool. During the machining process, the spindle speed is constant, so the optimum preload is mainly determined by the bearing load. When the external load is large, the systematic error is mainly caused by elastic deformation, so the optimal pre-tightening force is large to improve the rigidity of the system; when the load is small, the error is mainly caused by thermal deformation, and the optimal pre-tightening force is required. Smaller. The theoretical method for calculating the position of the optimal preload is not only calculated, but also the calculated value differs greatly from the actual value. Therefore, the determination of the optimal preload force requires a series of tests to obtain different working conditions. The relationship between the optimal preload force and the external load under the rapid temperature rise. In this paper, according to the 1000 type precision grinding machine spindle system, the series of rapid temperature rise load and other values ​​are obtained to obtain the best pre-tightening force.
3 Control principle When the spindle system changes the preload due to temperature rise and other speeds, the system should automatically adjust to the optimal value. When a load bearing is installed in the spindle system, the actual preload of the bearing can be determined from the picked up strain signal. The optimal pre-tightening force determined by the operating conditions parameters is the target. Adaptive control of the preload force can be achieved with a digital controller and corresponding actuator.
Reason. The pre-tightening force online servo control system is composed of a pre-tightening controller microcomputer and a stepping motor. The operating temperature parameters of the small-axis system real-time state are determined by the speed and temperature provided by the monitoring system to determine the system pre-tightening force. The left-hand position is controlled as the pull-in signal input pull-out path 10, and the stepping motor is rotated and rotated. The number of output angles of the 4 motor drives the piston pump piston to move the distance.
The pre-tightening force control ring end face elastic metal area is, the piston area is, then the displacement of the metal film is the axial bearing, that is, the outer ring axial movement of the bearing bearing, so that the actual pre-tightening, good preload, boat! The design adjustment of the micro, 4 control algorithm is mature for the continuous system technology, and it should be the most extensive. Considering that the wood system is realized in the elbow 0551 single-chip microcomputer 1, the following algorithm is used to simulate the adjustment system, and the proportional coefficient of the control method is still controlled; it is the integral time of the regulator, and 2 is the differential time of the regulator. .
In order to facilitate the realization of the microcomputer, the discretization of the formula 3, and the differential equation is used to replace the differential equation of the continuous system, the discrete one can be obtained, and the 10-bit type is the meter sample number, and the 0-step and 2-step scoreable constants.
The mechanism adopts a stepping motor and only needs an incremental signal. Therefore, in the control system of the formula 5, in order to avoid frequent movements and eliminate oscillation caused by frequent movements, a control system with a dead zone is adopted, and its control formula is adopted. For the dead zone 5 圮 adjustable parameters, the bits are small according to the control object. The 1 week movement is too complicated and complicated, and it is not easy to achieve the purpose of stabilizing the adjusted object. 5 value is too large, the system will produce a large lag. When the absolute value of the deviation 1 is 15, the control output is 0, and when it is 15, the result of the operation is output.
Parameter tuning directly affects the quality of the adjustment in the digital control system. The extended critical proportional method used in this paper is simple and practical. To set the parameters, the steps of the heart are as follows to find the critical proportionality and critical proportion cycle, that is, input the system, and carry out the proportional control, and gradually reduce the proportionality until the system produces the equal amplitude oscillation and the critical proportional period.
Select the degree of control, and find the value of 7 magic, a few by the control degree.
The critical oscillation period of 70V in the pure proportional action of 7VjJi is PkAr2, which is simplified to only one parameter. Change people. Observe the control effect until it is full.
5 system adjustment accuracy and parameter setting for the performance and accuracy of the 1 åž shaft system pre-tightening control, using the developed pre-tightening system to analyze and test the 10 type precision grinding.
In the control system. The step angle of the stepper motor is . 3, the transmission pitch of the gear pair 1 gear pair = 25, calculated to obtain the axial movement distance of each step of the motor rotation 04. From the positioning preload calculation formula 5 is the difference between the length of the inner and outer sleeves, the contact angle of the bearing, 夂For the total load deformation constant between the steel ball and the inner and outer raceways, Nmm 5. The adjustable value of the bearing preload is 1.7. Yes, the adjustment precision of the preload is very good.
Since the pressure of the controller is pushed by the gear and the screw drive to push the piston to pressurize, due to manufacturing errors and the like, several steps of idling may occur in order to overcome the gap when the stepping electric 1 rotates. Due to the incremental, 1 twist. This error has little effect on the accuracy of the system.
The parameter setting and response time are to ensure that the system can work stably and reliably according to the requirements, and the necessary test of the system parameters is carried out. The test procedure is as follows, take the sampling period to 18, start the test device, pre-work 2 mountain working conditions to determine the most pre-tightening force, to 4 magic, 1 change the proportional coefficient less than 1 to get the pre-tightening force with time function factory.
3. When the value is 19, the response time is 8, when the required pressure value is reached, and there is a small overshoot.
Due to the load variation and various factors during the working process of the machine tool, the preload of the spindle bearing will have a certain amplitude fluctuation and change near the actual preload value.
6 Conclusions On the basis of absorbing the advantages of existing pre-tightening controllers, a new pre-tightening controller has been developed, which has the characteristics of wide adjustment range, high response sensitivity and high precision, and low cost and low versatility. It has proven to be successful through industrial applications. In the paper, the control algorithm has the advantages of good stability, good response time and strong versatility. It can be used for single-chip microcomputers to form a single system, or it can be integrated with various types of precision machine tools or microcomputers in machining centers to make the best. Preload is achieved.
Gong Jianjun. On-line control of the preload force of the spindle bearing and its influence on the characteristics of the spindle system. Less 1.
Le Kexi, Quan Yongzhen, Zhou Guiru, and so on. Development of design method for load-bearing bearing Chen Zongnong, Guo 9. New preload force controller for precision machine tool spindle bearings
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