Abstract: An image forming apparatus including an image forming unit, a unit holder, and circuitry is provided. The image forming unit includes a color toner unit, a replaceable black toner unit, and a replaceable special toner unit that form a color toner image, a black toner image, and a special toner image, respectively. The unit holder selectively and detachably holds the replaceable black toner unit or the replaceable special toner unit. The circuitry controls the image forming unit to perform: a normal operation, when the unit holder holds the replaceable black toner unit, that forms a color-black image; a special operation, when the unit holder holds the replaceable special toner unit, that forms a color-special image; and a toner amount increase control that increases an amount of the color toner per unit area in the color toner image in the special operation than that in the normal operation.

Abstract: An image forming apparatus is provided. The image forming apparatus includes an image forming unit containing a special recording material and circuitry configured to control the image forming unit to form a hardly visible image on a recording medium with the special recording material. The hardly visible image is formed of a halftone dot image comprising isolated dots in a number smaller than that of isolated dots forming a visible image having the same image area ratio as the hardly visible image.

Abstract: An image forming apparatus including an image forming unit, a fixing device, and circuitry is provided. The image forming unit is configured to perform a special image forming operation that forms a color toner image and a special toner image with a color toner and a special toner, respectively, on a recording medium and a normal image forming operation that forms the color toner image without forming the special toner image on the recording medium. The fixing device is configured to fix the color toner image and the special toner image on the recording medium. The circuitry is configured to perform, in the special image forming operation, a toner amount suppression control that makes an amount of the color toner on the recording medium per unit area smaller than that in the normal image forming operation.

Abstract: A fixing device includes a nip formation pad disposed opposite an inner circumferential surface of an endless belt and a pressing rotary body pressed against the nip formation pad via the endless belt to form a fixing nip between the endless belt and the pressing rotary body, through which a recording medium is conveyed. The pressing rotary body has a diameter increasing from a center to each lateral end in an axial direction thereof. The nip formation pad includes a projection disposed downstream from a rotation axis of the pressing rotary body in a recording medium conveyance direction. The projection projects toward the pressing rotary body in an amount increasing from each lateral end to a center in a longitudinal direction of the nip formation pad parallel to the axial direction of the pressing rotary body.

Abstract: A fixing device includes a nip formation pad disposed opposite an inner circumferential surface of an endless belt and a pressing rotary body pressed against the nip formation pad via the endless belt to form a fixing nip between the endless belt and the pressing rotary body, through which a recording medium is conveyed. The pressing rotary body has a diameter increasing from a center to each lateral end in an axial direction thereof. The nip formation pad includes a projection disposed downstream from a rotation axis of the pressing rotary body in a recording medium conveyance direction. The projection projects toward the pressing rotary body in an amount increasing from each lateral end to a center in a longitudinal direction of the nip formation pad parallel to the axial direction of the pressing rotary body.

Abstract: An image forming apparatus includes an image carrier, a toner-image forming unit, a photosensor, an information obtaining unit, and a toner-amount calculating unit. The toner-image forming unit forms a toner image on the image carrier with toner. The photosensor detects a toner area where the toner is sticking to the image carrier. The information obtaining unit obtains particle-size-change information about how particle size distribution of the toner changes over time. The toner-amount calculating unit calculates a toner amount of the toner image based on the toner area and the particle-size-change information.

Abstract: An image forming apparatus includes an image carrier, a toner-image forming unit, a photosensor, an information obtaining unit, and a toner-amount calculating unit. The toner-image forming unit forms a toner image on the image carrier with toner. The photosensor detects a toner area where the toner is sticking to the image carrier. The information obtaining unit obtains particle-size-change information about how particle size distribution of the toner changes over time. The toner-amount calculating unit calculates a toner amount of the toner image based on the toner area and the particle-size-change information.

Abstract: 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.

Abstract: 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.