A controller is configured to control a print engine and a conveyor to form an image on both sides of a sheet. The controller is configured to: in a case where images to be formed on both sides of each of an Nth (N is a positive integer) sheet, an (N+1)th sheet, and an (N+2)th sheet are all monochrome image or all color image, convey the (N+2)th sheet to the print engine and form an image before forming an image on both sides of the (N+1)th sheet; and in a case where the images to be formed on both sides of each of the Nth sheet, the (N+1)th sheet, and the (N+2)th sheet are a mixture of the monochrome image and the color image, convey the (N+2)th sheet to the print engine and form an image after forming an image on both sides of the (N+1)th sheet.

A printing system performs first double-side printing when double-side printing is designated to a first print medium sides of which are distinguished from each other, and second double-side printing when the double-side printing is designated to a second print medium sides of which are not distinguished from each other, and a print page printed on a first surface set face-down when being fed out of a plurality of print pages included in print data is different between the first double-side printing and the second double-side printing.

An image-forming apparatus for forming an image on a sheet includes an image-forming unit that forms the image on the sheet, and a conveying unit that conveys the sheet on which the image is formed by the image-forming unit. The conveying unit includes a pair of first rollers that discharges the sheet to the outside of the image-forming apparatus and a pair of second rollers that conveys the sheet in a direction in which the sheet is discharged to the outside of the image-forming apparatus and that subsequently switches a conveyance direction of the sheet to an opposite direction to convey the sheet again to the image-forming unit. The pair of the first rollers and the pair of the second rollers partially overlap when viewed in a width direction of the sheet that is perpendicular to the conveyance direction of the sheet.

In an image forming apparatus capable of turning over a sheet to form images on both sides of the sheet, when duplex printing is executed successively on three or more sheets, a controller causes a first sheet conveyed from an image forming unit and a second sheet conveyed from the image forming unit to be guided into a first path by positioning a guide member in a first position, and then conveyed into a third path by a first roller, and causes a third and subsequent sheets conveyed from the image forming unit to be guided into a second path by positioning the guide member in a second position, and then conveyed into the third path by a second roller.

An image forming apparatus includes an image forming unit, a discharge unit, a double-sided conveyance path, a sheet plate, a skew correction unit, and a frame. The discharge unit discharges a sheet having an image from the image forming unit. The double-sided conveyance path conveys the sheet again to the image forming unit. The sheet plate restricts a position of an end, in a sheet width direction, of the sheet.

A sheet conveying apparatus includes a paper re-feeding path, a switching member, a reversing roller, a paper discharge roller, a motor, and a revolution control mechanism. The switching member can be switched between a first position and a second position. The reversing roller can reverse a revolving direction thereof between a first revolving direction and a second revolving direction. The paper discharge roller revolves in a third revolving direction for conveying the sheet in a third conveying direction. The motor reverses the revolving direction of the reversing roller and switches the position of switching member by reversing the revolving direction thereof. The revolution control mechanism revolves the paper discharge roller in the third revolving direction with the revolution of the motor, regardless of the reversing of the revolving direction of the motor.

After outputting a first start signal for causing an image forming unit to start formation of an image for a first side of an i-th sheet, a controller causes a feeding member to start feeding of the i-th sheet, and determines whether or not the i-th sheet has already been detected by a detector. In a case where the i-th sheet has been detected before a first predetermined time has elapsed, the controller outputs a second start signal for causing the image forming unit to start formation of an image for second side of an (i1)th sheet. In a case where the i-th sheet has not been detected before the first predetermined time has elapsed, the controller outputs the second start signal after the i-th sheet is detected.

The image forming apparatus includes a main body, a pick-up device to pick up a printing medium, a developing device to develop an image on a side of the printing medium picked up by the pick-up device, a fixing device to fix the image developed on the side of the printing medium, a paper reverse device to guide the printing medium from a transfer direction of the printing medium passing through the fixing device, through a reverse path to the developing device and the fixing device, to develop and fix another image on other side of the printing medium, a discharging device to discharge the printing medium outside the main body, a post-processing device provided in the main body, and a post-processing path selection device rotatable to a first position to guide the printing medium through a discharge path to guide the printing medium passing through the fixing device to the discharging device and a second position to guide the printing medium from the discharge path to a post-processing path branched from the discharge path, to guide the printing medium to the post-processing device.

An image forming apparatus includes an image forming unit, a discharge unit, a double-sided conveyance path, a sheet plate, a skew correction unit, and a frame. The discharge unit discharges a sheet having an image from the image forming unit. The double-sided conveyance path conveys the sheet again to the image forming unit. The sheet plate restricts a position of an end, in a sheet width direction, of the sheet. The skew correction unit obliquely conveys the sheet to abut the sheet end. The frame determines a position of the sheet plate and includes a first positioning portion to position a sheet plate first positioned portion and a second positioning portion to position a sheet plate second positioned portion with the skew correction unit between the first and second positioned portion. The first positioning portion faces the first positioned portion and the second positioning portion faces the second positioned portion.

An image forming apparatus including an image forming portion, a fixing device, a pressure switching mechanism, and a controller. The fixing device includes a fixing member, a heating portion, and a pressing member. The pressure switching mechanism is configured to switch pressure between the fixing member and the pressing member. The controller is configured to execute an operation in an image forming mode in which the image is capable of being formed on an envelope. The controller is configured to cause the pressure switching mechanism to switch the pressure to a first pressure when an instruction to form the image on an address side of the envelope is inputted and to cause the pressure switching mechanism to switch the pressure to a second pressure when an instruction to form the image on a non-address side of the envelope is inputted. The second pressure is higher than the first pressure.