An image forming device includes a transfer unit that transfers a toner image onto a recording medium that has first and second surfaces and is conveyed in a conveyance direction; a main heating unit arranged downstream of the transfer unit in the conveyance direction, and which contacts and heats the recording medium and fixes the toner image onto the recording medium; a reversing unit that reverses front and back of the recording medium having a first toner image fixed onto the first surface; and a preheating unit arranged between the transfer and main heating units in the conveyance direction and that heats the recording medium having a second toner image transferred onto the second surface. The preheating unit heats the recording medium so that a temperature of the first surface is lower than a softening point of a toner before the recording medium is heated by the main heating unit.

An image forming apparatus sets, in a case where a mode for executing a heating process a plurality of times is set, a target temperature of a fixing unit during a second heating process depending on image information about a toner image to be formed on a first surface of a recording medium immediately before a first heating process.

A fixing device includes: a heating section that heats in a non-contact manner a front surface of a recording medium; a feeding section that feeds the recording medium while causing the front surface to be opposed to the heating section; and a maintaining section that, in order to enable the recording medium to be fed by the feeding section while a rear surface that is opposite to the front surface, and that is in an image region where an unfixed-image is formed on the front surface is in a non-contact state, maintains the non-contact state.

An image forming apparatus includes an image bearing member configured to bear a non-fixed toner image, a transfer portion configured to transfer the non-fixed toner image onto a sheet at a transfer nip, a fixing portion including a first rotary member, a second rotary member and a heating portion configured to heat the first rotary member, a control portion configured to execute a nip image forming process of forming a nip image, on the sheet, corresponding to a shape of the fixing nip, and a reading unit configured to read the nip image, wherein the control portion sets the heating portion to a first temperature in a case where the non-fixed toner image passes through the fixing nip and sets the heating portion to a second temperature which is lower than the first temperature in a case where the nip image passes through the fixing nip.

Even from a plurality of small documents, their front-side and back-side images to be formed on a recording paper sheet, with alignment and coincidence of the front-side and back-side images of each document between the front and back sides of the recording paper sheet. In an image forming apparatus, an image processing section detects a front-side image of an original document from a scan area read in a first scan by an image reading section, detects a back-side image of the original document from a scan area read in a second scan, and moves or rotates the front-side image and the back-side image of the original document in terms of a whole image of the scan area so that the front-side image and the back-side image of the original document are brought into alignment and coincidence between a front side and a back side of a recording paper sheet.

A duplex printing method includes, determining an amount of shrinkage of a media sheet onto which a front side image has been printed; scaling an image to be printed on a back side of the sheet with a scaling function that depends upon the determined shrinkage; and printing the scaled image on the back side of the sheet. The step of determining includes predicting a shrinkage of a media sheet on the basis of process parameters, and on the basis of a model that is defined by a set of model parameters and that describes a dependence of the shrinkage on the process parameters, the process parameters including at least an amount of marking material to be applied to the front side of the sheet; measuring an actual shrinkage of the sheet; and adjusting the model parameters based on a comparison between the predicted shrinkage and the measured shrinkage to improve a prediction of a shrinkage for a subsequent sheet.

An image forming device, includes: a transfer unit that transfers a toner image onto a recording medium being conveyed; a main heating unit that is disposed at a downstream side of the transfer unit in a conveyance direction of the recording medium, heats the recording medium in contact with the recording medium, and fixes the toner image to the recording medium; a reversing unit that reverses front and back of the recording medium having the toner image fixed on a first surface of the recording medium by the main heating unit, and sends the recording medium to the transfer unit; a preheating unit that is arranged between the transfer unit and the main heating unit in the conveyance direction of the recording medium and heats the recording medium in a non-contact state, the preheating unit being configured to heat the recording medium so that, when the recording medium that is sent to the transfer unit by the reversing unit and on which the toner image is transferred to a second surface is heated, a temperature of the first surface of the recording medium is higher than a softening point of a toner before the recording medium is heated by the main heating unit; and a non-contact unit that brings a toner image forming region on the first surface of the recording medium on which the toner image is transferred onto the second surface and a member other than the recording medium between the preheating unit and the main heating unit in a non-contact state.

An image forming device includes a transfer unit that transfers a toner image onto a recording medium that has first and second surfaces and is conveyed in a conveyance direction; a main heating unit arranged downstream of the transfer unit in the conveyance direction, and which contacts and heats the recording medium and fixes the toner image onto the recording medium; a reversing unit that reverses front and back of the recording medium having a first toner image fixed onto the first surface; and a preheating unit arranged between the transfer and main heating units in the conveyance direction and that heats the recording medium having a second toner image transferred onto the second surface. The preheating unit heats the recording medium so that a temperature of the first surface is lower than a softening point of a toner before the recording medium is heated by the main heating unit.

An image forming apparatus includes an image forming unit that forms an image on a recording medium, a reversal transport unit that reverses front and back sides of the recording medium having an image formed by the image forming unit, and then transports the recording medium to the image forming unit, a detection unit disposed in a transport path of the reversal transport unit to detect the position of the recording medium in a transverse direction transverse to a transport direction, the transport direction being the direction of transport of the recording medium, and an adjustment unit that adjusts the position of an image in the image forming unit in accordance with the position of the recording medium detected by the detection unit.

An image forming apparatus employing an electrophotographic image forming unit and an inkjet image forming unit, thereby being capable of printing an image on each of a front surface and the back surface of a recording medium.