Ricoh Company, Ltd.

Sumiaki Aoki

Koichi Kudo

Nobuyuki Baba

Toshiharu Murai

Takashi Kimura

Toshihito Kamei

Tatsuhiko Oikawa

Kohta Akiyama

Mikio Ohashi

Kaoru Satoh

An image forming apparatus includes: a recording head including multiple nozzles and multiple piezoelectric elements that generate pressure for causing droplets to be ejected from the nozzles; a driving-waveform generating unit that generates a driving waveform to be applied to the piezoelectric elements; first switching devices each disposed between the driving-waveform generating unit and respective one of the piezoelectric elements; second switching devices each disposed between a predetermined voltage and respective one of the piezoelectric elements; and a slight-vibration control unit. The slight-vibration control unit causes slight vibrations to be applied to a non-ejection nozzle by placing the second switch device for the non-ejection nozzle in a conduction state, and, when a predetermined period of time has elapsed after shift to the conduction state, placing the second switch device in a non-conduction state and the first switch device for the non-ejection nozzle in a conduction state.

Image forming apparatus

An image forming device includes a liquid discharge head including piezoelectric elements; a drive waveform generating unit that outputs a drive waveform; a selection unit that applies the drive waveform to the piezoelectric elements; a resonant frequency adjusting circuit that is connected in parallel with the piezoelectric elements; a switch unit that switches the resonant frequency adjusting circuit; and a switching control unit that causes the switch unit to switch in accordance with a first number of simultaneously driven piezoelectric elements. When the first number of the simultaneously driven piezoelectric elements is greater than a predetermined number, the switching control unit connects the resonant frequency adjusting circuit, so that a resonant frequency of a closed loop becomes lower than a resonant frequency of the closed loop when the first number of the simultaneously driven piezoelectric elements is less than the predetermined number.

Image forming device

There is provided a head control device able to re-charge an electromechanical transducing element with a driving pulse without requiring an additional re-charging time period in a recording period. The driving signal includes a plurality of driving pulses, and in each recording period, at least one driving pulse includes a portion varying from a discharging level to a medium level to charge the piezoelectric element to eject a liquid droplet, and a subsequent portion varying from the medium level to a target level to re-charge the piezoelectric element to the target level.

Head control device and image recording apparatus

A head driving unit the generates a driving waveform, each driving waveform including a plurality of driving pulses, and selects one or more driving pulses to be applied to a liquid drop discharging head in response to data corresponding to an image. By selecting a plurality of selection signals that defines the driving pulses to be applied to the liquid discharging head, the head driving unit can change a recording density or record multiple value images.

Head driving unit and an image forming apparatus using the same

A document sensing device for an image forming apparatus of the present invention is capable of sensing a document stably without being influenced by disturbing light, e.g., light ascribable to fluorescent lamps or similar illuminators illuminating a room. According to one aspect of die invention, optical elements are held by a jig rotatable about an optical axis. According to another aspect of the invention, a light receiving means or a photosensor means has at least four light-sensitive regions.

Document sensing device for an image forming apparatus

An original placement table is provided, on which an original sheet is placed. An original scanning device causes a light beam to scan the original sheet placed on the original placement table. A light receiving device receives a light beam which has been reflected by the original sheet placed on the original placement table after being emitted by the original scanning device. An original edge determining device monitors light intensity of the light beam received by the light receiving device. The original edge determining device determines that the light beam currently being received by the light receiving device is the light beam reflected by an edge of the original sheet placed on the original placement table when a significant variation is detected in the light intensity either for the first time or for the last time in one scanning operation of the original scanning device.

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Kanagawa, Japan

Sumiaki Aoki