Research On Closed-loop Control Device Of Bolt Preloading Torque

Preload torque is an important parameter for bolt support,which directly affects the quality of roadway support.At present,the coal mine adopts a pneumatic bolt rig as a torque applying machine,and a torque multiplier with a certain magnification is connected to the output shaft of the bolt rig to amplify the torque.The fact that the torque multiplier output torque is as high as 800N·m and the fluctuation is large.,seriously affect the effect of bolt support.Therefore,it is necessary to control the torque of the bolt.Aiming at the problems that the current coal bolt torque is uncontrollable and the bolt pre-tightening torque control method has complex structure,low operability and low control precision,a bolt pre-tightening torque control method is proposed.The method is based on the transmission relationship between the torque multiplier gears and the relationship between the pressure and the torque,and fixes the bolt pre-tightening torque control device to the torque multiplier handle setting position,and the torque is reached by measuring the torque multiplier ring gear torque.Real-time control.Firstly,the theoretical analysis of the transmission efficiency of the torque multiplier is carried out.It turns out that the coal surface enters the torque multiplier,causing friction between the gears,resulting in a decrease intransmission efficiency and a torque loss of up to 160 N·m.If the ring gear torque is measured,the torque loss and fluctuation caused by the torque multiplier transmission efficiency can be greatly reduced.Then,the principle of closed-loop control device for bolt pre-tightening torque is proposed,and the main part of the device is designed with liquid-filled bellows and slide valve.The bellows is used as part of measuring torque to ensure the accuracy and reliability of measurement.On the basis of relevant parameter design,the corrugated pipe is selected reasonably,and the strength and stiffness are simulated and analyzed.The sensitivity factors affecting the measurement such as temperature and angle are experimentally verified.The spool valve is designed based on the relevant parameters of the bellows,and its reliability is verified by simulation.Finally,the AMESim model of the bolt torque closed-loop control device is established,and the influence of the torque multiplier transmission efficiency,the friction coefficient between the nut and the bolt thread,and the friction coefficient of the ball mat on the control result of the torque control device are considered.The experimental platform of the anchor torque closed-loop control device was built and verified by the downhole test.The results show that the environment adaptability of the device is strong,and the temperature and angle have no influence on the control result;the transmission efficiency of the torque multiplier,the friction coefficient between the nut and the anchor thread,and the friction coefficient of the ball pad respectively make the maximum error of thetorque control device respectively 6.2%,12%,10%,acceptable compared to the control results.Therefore,the device can effectively control the torque of the bolt at 470-510 N·m,and the response is fast and the reliability is high.