Hitachi Koki Co., Ltd.

Hitachi, Ltd.

Keiji Kunimi

Kazuo Shimizu

Masatoshi Sakata

Yukio Yamamoto

Takashi Sekino

Tatunari Sato

A piezoelectric type ink recording device has piezoelectric elements for ejecting ink droplets. Variation can exist in characteristics of the piezoelectric elements that results in variation in speed at which the piezoelectric elements eject ink droplets. In order to suppress this variation in ejection speed, the ink recording device has a driver shared by all of the piezoelectric elements and a separate discharge control circuit for each piezoelectric element. The driver shared and the separate discharge control circuits output pulses to the piezoelectric elements in synchronization. Each piezoelectric element starts discharging its charge in synchronization with the falling edge of a drive pulse from the driver. As a result, the piezoelectric elements deform during the falling edge of the drive pulse to increase volume of corresponding ink chambers, thereby drawing ink into the ink chambers. However, each piezoelectric element continues discharging for a time determined by the width of the pulse from the corresponding discharge control circuit. In this way, the amount of charge discharged from each piezoelectric element can be individually regulated by changing the pulse waveform applied to each piezoelectric element by the corresponding discharge control circuit.

Ink jet printer using piezoelectric elements with improved ink droplet impinging accuracy

In transferring color image data having a tone on a recording paper, a threshold matrix data for adjusting the tone is selected in accordance with the image data having a dot arrangement. The threshold conversion curve of the threshold matrix data selected is used to correct a variation in the tone of the image data due to mechanical and electrical variations in a color image transferring apparatus including variations in the rotation speed of a transferring drum, a power source voltage to be applied to a transferring head and a relative position between the transferring drum and the recording paper. This correction can achieve improved transference of the image data on the recording paper.

Color image transferring method and apparatus

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Katsuta, Japan

Keiji Kunimi