The working principle of the torque wrench is that after the motor is decelerated by the planetary gear mechanism, the power is transmitted to the impact head, and the two convex heads of the impact head drive the pull shaft to rotate through the pull shaft claw, and the pull shaft completes the power output.

那么扭力扳手使用一段時(shí)間后不可避免會(huì)出現(xiàn)輸出動(dòng)力下降的現(xiàn)象，隨著扳手的使用時(shí)間的增加，輸出動(dòng)力將繼續(xù)下降，直無(wú)法工作。

Then the torque wrench will inevitably decline in output power after a period of use. With the increase of wrench use time, the output power will continue to decline until it can not work.

技術(shù)人員通過(guò)對(duì)電動(dòng)扭力扳手的解體觀察，發(fā)現(xiàn)所有使用過(guò)的扭力扳手，其扳軸工作面無(wú)一例外地發(fā)生了嚴(yán)重磨損。磨損后的工作面是與原工作面成大約45度角的一個(gè)斜面，這個(gè)斜面在工作中將使作用在扳軸上的沖擊力分散。沖擊力分散后，扭力扳手內(nèi)部各部件的受力情況也隨之改變。

The technicians found that the working face of the wrench shaft of all the used torque wrenches was severely worn without exception through the disassembly and observation of the electric torque wrench. The worn working face is an inclined plane with an angle of about 45 degrees with the original working face, which will disperse the impact force acting on the wrench shaft. After the impact force is dispersed, the stress situation of the internal parts of the torque wrench will also change.

通過(guò)以上的觀察結(jié)論，我們找出了電動(dòng)扳手失效的主要原因-------扳軸工作面的嚴(yán)重磨損。所以說(shuō)要有效延長(zhǎng)電動(dòng)扳手的使用壽命，就一定要磨損問(wèn)題，并且由于扳軸磨損比沖擊頭要更嚴(yán)重，所以，扳軸磨損的問(wèn)題是關(guān)鍵。若此問(wèn)題得以，沖擊頭磨損問(wèn)題也就迎刃而解了。將整體式的扳軸改為拆分式的，扳軸的工作面可以拆卸，在使用一段時(shí)間后，可視其磨損情況進(jìn)行更換。活動(dòng)工作面可單獨(dú)選用適合的材料，通過(guò)合理的加工工藝過(guò)程，達(dá)到較高的機(jī)械性能。

Through the above observation conclusion, we find out the main cause of the failure of the electric wrench - the serious wear of the working face of the wrench shaft. Therefore, in order to effectively extend the service life of the electric wrench, it is necessary to solve the problem of wear, and since the shaft wear is more serious than the impact head, the shaft wear is the key. If this problem can be solved, the problem of impact head wear will be solved. Change the integral pull shaft to the split type, and the working surface of the pull shaft can be disassembled. After a period of use, it can be replaced according to its wear condition. Suitable materials can be selected independently for the movable working face, and high mechanical properties can be achieved through reasonable processing process.

因此選用高碳鋼，進(jìn)行先淬火后中溫回火的熱處理工藝。這樣加工后的活動(dòng)工作面既有較高的硬度又有一定的韌性，使其在經(jīng)受沖擊時(shí)不會(huì)發(fā)生斷裂，且可以進(jìn)行大批量的加工，一次加工即可滿(mǎn)足長(zhǎng)期更換的使用要求，非常方便。而電動(dòng)扳手失效的問(wèn)題也就迎刃而解。

Therefore, high carbon steel is selected for the heat treatment process of first quenching and then medium temperature tempering. In this way, the working face after machining has high hardness and certain toughness, so that it will not break when it is impacted, and can be processed in large quantities. One processing can meet the use requirements of long-term replacement, which is very convenient. And the problem of electric wrench failure is solved.