| 摘要 |
In an impulse wrench there is provided an impulse unit ( 13 ) with a motor driven inertia drive member ( 14 ), and a movement detecting device ( 16 ) arranged to detect the angular movement of the inertia drive member ( 14 ), wherein the movement detecting device ( 16 ) comprises a rotating disc ( 17 ) rigidly connected to and co-rotating with the inertia drive member ( 14 ), and a sensing device ( 19 ) including four Hall-element type sensors ( 120 a-d), and the disc ( 17 ) having a rim portion ( 18 ) which is magnetised to provide a number of magnetic poles for activating the sensors ( 120 a-d) at rotation of the inertia drive member ( 14 ), wherein the sensors ( 120 a-d) are arranged in pairs such that the delivered signals from the sensors in each pair has a relative phase lag of 180 degrees, whereas the sensors of one of the pairs ( 120 a,c) are arranged to deliver signals with a phase lag of 90 degrees relative to the sensor signals from the other pair ( 120 b,d).
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