Patent ID: 7828072

Claim:
An impact tool comprising: a motor; an output shaft rotated by said motor; a hammer for intermittently providing an impact force to said output shaft; a hammer holder for movably holding said hammer; an impact force generator for converting an output of said motor into a reciprocating motion of said hammer to generate the impact force; and an air chamber formed between said hammer and said hammer holder such that a volume of said air chamber is variable in response to a position of said hammer relative to said hammer holder; wherein the impact tool further comprises a biasing unit configured to apply a bias force to said hammer in a direction toward said output shaft, thereby increasing the impact force in cooperation with an air pressure caused by a volume change of said air chamber, wherein said hammer holder is movably supported by a housing of the impact tool, and biased in the direction toward the output shaft against said housing by said biasing unit, so that said hammer indirectly receives the bias force for directing said hammer toward said output shaft through said hammer holder.