| 摘要 |
FIELD: process engineering.SUBSTANCE: invention relates to hand tools. Drive tool comprises working tool drive motor, rpm control switch displaced by the user, top extreme position controller of rpm switch displacement and controller of the strength of current fed to motor by PDM-signal duty factor proceeding from amount of depressing of rpm control switch. Control unit increases motor rpm in compliance with said amount of depressing of rpm control switch. Preset number of PDM-signal duty factors is set for every step of depressing. Relationship between the preset number of PDM-signal duty factors and said amount of depressing of rpm control switch is larger at first step whereat top extreme position is smaller than that at steps other than the first one. Control unit controls the PDM-signal duty factor at, at least first step, so that rpm increases when amount of depressing of rpm control switch increases to top extreme position. Control unit controls the PDM-signal duty factor when magnitude of manipulation decreases from top extreme position to preset position by hysteresis characteristic whereat rpm stays constant unless the amount of depressing of rpm control switch reaches the preset position.EFFECT: higher precision of motor rpm control.3 cl, 13 dwg |
