Torque control method for numerical control constant torque electric wrench and electric wrench

Abstract

The invention discloses a numerical-control electric definite-torque wrench and a torque control method thereof. The method includes the steps of firstly, setting a preset torque value and transmitting the preset torque value to a control circuit; secondly, allowing the control circuit to power a wrench motor through an electronic switch so as to drive the wrench motor to rotate and output torque through a reduction mechanism; thirdly, allowing the control circuit to detect speed of the wrench motor, and comparing the speed with the preset torque value; and fourthly, when the satisfactory required value is obtained, powering off the wrench motor through the electronic switch. By using speed data of the wrench motor as a control key point, control resolution is increased, and three mutually covering operation torque curves can be created for the motor. Original smooth torque curves are converted into steep torque range curves, the difference between the initial torque and the overload torque is enlarged, and accordingly range and precision of control output are increased greatly.

Description

technical field [0001] The invention relates to a constant torque wrench and a torque control method thereof, in particular to a torque control method for a numerically controlled constant torque electric wrench and the electric wrench. Background technique [0002] Generally, the fastening of high-strength bolts requires initial tightening and then final tightening, and each step requires strict torque requirements. The initial tightening and final tightening of large hexagonal high-strength bolts must use a constant torque wrench. The electric torque wrench is a booster wrench composed of an electric motor and a star-shaped gear set. It has small size, light weight, fast unlocking speed, and the maximum torque can reach 20000Nm. It is a more efficient and economical choice than a hydraulic wrench. It can excellently complete the task of loading and unloading large-diameter bolts and nuts. Like a hydraulic wrench, it has no impact, and its tightening and dismounting speed...

AI Technical Summary

Problems solved by technology

[0005] Although this simple current control is relatively simple, it is under the ideal relationship between current and torque. However, it has been found through research that the fluctuation and change of the output torque are greatly affected by the speed of the wrench motor, and the wrench motor As a current-type load, the current does not change significantly or basically does not change when the working torque fluctuates slightly

That is to say, in actual working conditions, when the output torque is small, the torque variation range is large and the current variation range is small. When the high torque control output is controlled, the torque variation range is small and the current variation range is large, especially when the wrench motor is fully loaded Or when overloaded, the relationship between the torque curve and the current curve function is very complicated! Moreover, when starting, the wrench motor is static, and the starting current is very large, which is 5 to 7 times that of normal operation, covering almost the current value of all torque output ranges. Just capturing the current will cause the protection to stop when starting up! In addition, when the bolt is actually tightened, because a thread of the bolt has a processing defect, or foreign matter such as fine sand is embedded in the thread, the current of the wrench motor will suddenly increase, resulting in a detection error! Therefore, it has the following disadvantages. The constant torque wrench adopting the current component control technology can only realize the rough step-by-step control of the torque, the control accuracy is low, and it cannot realize the stepless adjustment of the torque output, and its anti-interference ability is poor.

Therefore, the existing ones usually use the segment switch to set the preset torque, so it is far from meeting the requirements of high-precision working conditions

[0006] In addition, because the instantaneous current capture detection accuracy cannot meet the previous current control, it is found that when the current changes by hundreds of milliamperes, the linearity of the torque acting on the different working condition curves of the wrench motor is inconsistent, that is to say, in the control output When the torque is small, the current rises quickly, but the torque change is not obvious, but when the high torque is output, the torque changes quickly, and at the same time, the amplitude of the current change is also large, or even doubled. high difficulty

Images