Patent ID: 8540343

Claim:
An image forming apparatus comprising: a liquid ejection head having an ejection surface in which a plurality of nozzles that eject liquid droplets are arranged two-dimensionally; a conveyance device which conveys a recording medium on which the liquid droplets ejected from the plurality of nozzles of the liquid ejection head are deposited; a main body frame which supports the conveyance device; a head movement device which supports the liquid ejection head movably with respect to the main body frame; and a head fixing device which fixes the movable liquid ejection head to the main body frame at a position for droplet ejection onto the recording medium, wherein: the head fixing device has a pressure application device for head fixing which impels the liquid ejection head in a width direction of the recording medium which is perpendicular to a conveyance direction in which the conveyance device conveys the recording medium, and wherein a spring constant of the pressure application device for head fixing and a mass of the liquid ejection head are set so that a resonance (f 1 ) satisfies formula (1) below: f 1 =(2π) −1 ×( k 1 /m 1 ) 1/2 (1) where f 1 is the resonance frequency, k 1 is the spring constant of the pressure application device for head fixing, m 1 is the mass of the liquid ejection head; wherein the resonance frequency (f 1 ) is different from a component of a vibration pitch which is dependent on a spatial distance in the conveyance direction between a pair of nozzles which correspond to a joint section of a nozzle alignment forming adjacent dots in the width direction on the recording medium, of distances between nozzles in the conveyance direction in nozzle arrangement of the liquid ejection head, a relative vibration in the width direction between the conveyance device and the liquid ejection head during conveyance of the recording medium, and a conveyance speed at which the conveyance device conveys the recording medium, and wherein a condition represented by formula (2) below is met: |sin{π· OSy·fv/vp }|≦¼ (2) where OSy is the spatial distance, fv is the relative vibration frequency, and vp is the conveyance speed.