Abstract: A fixing device includes: a rotatable member including an electroconductive layer; a helical coil having a helical axis direction along a generatrix direction of said rotatable member; a magnetic member not forming a loop outside the electroconductive layer; a frequency setting portion for setting a frequency of an AC current caused to flow through said coil; and a temperature detecting portion for detecting a temperature of said rotatable member, including a first temperature detecting member and a second temperature detecting member. The electroconductive layer generates heat through electromagnetic induction heating by magnetic flux resulting from the AC current, and an image is fixed on a recording material by heat of said rotatable member. The frequency setting portion sets the frequency depending on a value of a difference between a detection temperature of said first temperature detecting member and a detection temperature of said second temperature detecting member.

Abstract: The image forming apparatus includes an image processing section that converts image data into pixel data, an image forming section that forms a toner image based on the pixel data, and a fixing section that fixes the toner image to the recording material by heating the recording material with the toner image formed thereon while conveying the recording material through a nip portion, wherein the image processing section divides the pixel data corresponding to one recording material into a plurality of areas each formed of a predetermined number of pixels and acquires density information on some of the pixels within each of the areas as representative values, wherein the fixing section carries out a process of fixing the toner image for which the density information has been acquired, under a fixing condition according to a maximum value of the representative values.

Abstract: An image forming apparatus for forming an image on a recording material by a plurality of color materials, the apparatus includes: a determination unit configured to determine, based on converted data that are converted from image data corresponding to each image formed by the plurality of color materials, values each relating to an area of a respective color material caused to adhere to a recording material; and a detection unit configured to detect, based on the values each relating to the area of the respective color material that the determination unit determines, an overlapping of color materials.

Abstract: The image forming apparatus includes an image processing section that converts image data into pixel data, an image forming section that forms a toner image based on the pixel data, and a fixing section that fixes the toner image to the recording material by heating the recording material with the toner image formed thereon while conveying the recording material through a nip portion. The image processing section divides the pixel data corresponding to one recording material into a plurality of areas each formed of a predetermined number of pixels and acquires density information on some of the pixels within each of the areas as representative values. The fixing section carries out a process of fixing the toner image for which the density information has been acquired, under a fixing condition according to a maximum value of the representative values.

Abstract: A fixing apparatus includes: two rotatable members, for forming a nip, including a region where an outer diameter is increased from a longitudinal central portion toward a longitudinal end portion; a heater; and a controller for controlling a heat generation distribution of the heater. The controller is capable of controlling the heater so that the heat generation distribution of the heater is such that a heat generation amount at the longitudinal end portion is larger than that at the longitudinal central portion in a period from start of the heater until the recording material reaches the nip. A ratio of the heat generation amount at the longitudinal end portion to that at the longitudinal central portion is larger when a cumulative amount of use of the fixing apparatus is larger than a predetermined amount than when the cumulative amount of use is smaller than the predetermined amount.

Abstract: Adjusting the start timing for conveying a printing material from a printing material conveying unit based on a power supply update period for power supplied to a heater allows proper power correction timing to be attained for compensating for a drop in temperature of the endless belt following the printing material entering a fixing nip portion.

Abstract: The image forming apparatus includes a fixing portion, a temperature detection element, and a power control portion. The power control portion is capable of setting a first power supply control mode for supplying power according to the detected temperature for each one control cycle, a second power supply control mode for supplying power according to the detected temperature for each one control cycle and a third power supply control mode for supplying predetermined power, and switches, immediately before a leading edge of the recording material enters the fixing portion, a state of supplying the power in the first power supply control mode to a state of supplying the power in the second power supply control mode, and then switches the state of supplying the power in the second power supply control mode to a state of supplying the power in the third power supply control mode.

Abstract: Corrected power for compensating for a reduction in the temperature of an endless belt that accompanies the entry of a recording material into a fixing nip portion is adjusted by correcting the power supplied to a fixing unit when the recording material enters the fixing unit with a correction power based on the difference between the update time of a power updating period and the time of the entry of the recording material.

Abstract: The present invention provides an image forming apparatus including an upstream conveying portion, a downstream conveying portion, and a loop detector, wherein the image forming apparatus further includes a driving portion which moves the contact portion to a projecting position where the sheet conveying path is in contact with a conveyed sheet and to a retracted position where the sheet conveying path is not in contact with the conveyed sheet, and a controlling portion which controls the driving portion such that the contact portion is moved from the projecting position to the retracted position before a tip end of a sheet which enters the sheet conveying path from the upstream conveying portion reaches the contact portion.

Abstract: The image forming apparatus includes an image forming portion forming a toner image on a recording material, and a fixing portion heating and fixing the toner image formed on the recording material to the recording material, wherein the apparatus has a cleaning mode in which the fixing portion is cleaned, and when the cleaning mode is set, the image forming portion forms a predetermined toner image on the recording material, and the fixing portion then heats and fixes the predetermined toner image to the recording material to form a cleaning sheet which is heated and conveyed to clean the fixing portion. By the virtue of the present invention, it achieves high cleaning performance in which the fixing portion is cleaned by the cleaning sheet.

Abstract: The image forming apparatus includes an image processing section that converts image data into pixel data, an image forming section that forms a toner image based on the pixel data, and a fixing section that fixes the toner image to the recording material by heating the recording material with the toner image formed thereon while conveying the recording material through a nip portion, wherein the image processing section divides the pixel data corresponding to one recording material into a plurality of areas each formed of a predetermined number of pixels and acquires density information on some of the pixels within each of the areas as representative values, wherein the fixing section carries out a process of fixing the toner image for which the density information has been acquired, under a fixing condition according to a maximum value of the representative values.

Abstract: The image forming apparatus includes a fixing portion, a temperature detection element, and a power control portion. The power control portion is capable of setting a first power supply control mode for supplying power according to the detected temperature for each one control cycle, a second power supply control mode for supplying power according to the detected temperature for each one control cycle and a third power supply control mode for supplying predetermined power, and switches, immediately before a leading edge of the recording material enters the fixing portion, a state of supplying the power in the first power supply control mode to a state of supplying the power in the second power supply control mode, and then switches the state of supplying the power in the second power supply control mode to a state of supplying the power in the third power supply control mode.

Abstract: A fixing apparatus includes: two rotatable members, for forming a nip, including a region where an outer diameter is increased from a longitudinal central portion toward a longitudinal end portion; a heater; and a controller for controlling a heat generation distribution of the heater. The controller is capable of controlling the heater so that the heat generation distribution of the heater is such that a heat generation amount at the longitudinal end portion is larger than that at the longitudinal central portion in a period from start of the heater until the recording material reaches the nip. A ratio of the heat generation amount at the longitudinal end portion to that at the longitudinal central portion is larger when a cumulative amount of use of the fixing apparatus is larger than a predetermined amount than when the cumulative amount of use is smaller than the predetermined amount.

Abstract: The image forming apparatus, in the case where image forming is performed on a recording medium whose size covers a position of a second temperature detection element perpendicularly disposed to the recording medium conveyance direction, when the detected temperature rises to a predetermined temperature during execution of the first power supply control, a first power supply control is switched to a second power supply control. In the case where image forming is performed on a recording medium whose size does not cover a position of the second temperature detection element, when the detected temperature rises to a predetermined temperature during execution of the first power supply control, a conveyance control portion executes a control for extending the conveyance interval of the recording medium. Thus, an unduly large temperature rise in the non-sheet passing portion is prevented, and a good quality image can be provided without glossy unevenness in one sheet.

Abstract: Corrected power for compensating for a reduction in the temperature of an endless belt that accompanies the entry of a recording material into a fixing nip portion is adjusted by correcting the power supplied to a fixing unit when the recording material enters the fixing unit with a correction power based on a difference between the update time of a power updating period and the time of the entry of the recording material.

Abstract: Adjusting the start timing for conveying a printing material from a printing material conveying unit based on a power supply update period for power supplied to a heater allows proper power correction timing to be attained for compensating for a drop in temperature of the endless belt following the printing material entering a fixing nip portion.

Abstract: The image forming apparatus, in the case where image forming is performed on a recording medium whose size covers a position of a second temperature detection element perpendicularly disposed to the recording medium conveyance direction, when the detected temperature rises to a predetermined temperature during execution of the first power supply control, a first power supply control is switched to a second power supply control. In the case where image forming is performed on a recording medium whose size does not cover a position of the second temperature detection element, when the detected temperature rises to a predetermined temperature during execution of the first power supply control, a conveyance control portion executes a control for extending the conveyance interval of the recording medium. Thus, an unduly large temperature rise in the non-sheet passing portion is prevented, and a good quality image can be provided without glossy unevenness in one sheet.

Abstract: The image forming apparatus, in the case where image forming is performed on a recording medium whose size covers a position of a second temperature detection element perpendicularly disposed to the recording medium conveyance direction, when the detected temperature rises to a predetermined temperature during execution of the first power supply control, a first power supply control is switched to a second power supply control. In the case where image forming is performed on a recording medium whose size does not cover a position of the second temperature detection element, when the detected temperature rises to a predetermined temperature during execution of the first power supply control, a conveyance control portion executes a control for extending the conveyance interval of the recording medium. Thus, an unduly large temperature rise in the non-sheet passing portion is prevented, and a good quality image can be provided without glossy unevenness in one sheet.

Abstract: The image forming apparatus includes an image forming portion forming a toner image on a recording material, and a fixing portion heating and fixing the toner image formed on the recording material to the recording material, wherein the apparatus has a cleaning mode in which the fixing portion is cleaned, and when the cleaning mode is set, the image forming portion forms a predetermined toner image on the recording material, and the fixing portion then heats and fixes the predetermined toner image to the recording material to form a cleaning sheet which is heated and conveyed to clean the fixing portion. By the virtue of the present invention, it achieves high cleaning performance in which the fixing portion is cleaned by the cleaning sheet.

Abstract: The present invention provides an image forming apparatus having an upstream conveying portion, a downstream conveying portion, and a contact loop detection portion to detect a loop of the sheet formed between the upstream conveying portion and the downstream conveying portion, wherein the loop detection portion, includes a sensor that outputs the detection signal, a contact portion that protrudes into a sheet conveyance path between the upstream conveying portion and the downstream conveying portion as if to come into contact with the sheet conveyed through the sheet conveyance path and causes the sensor to output the detection signal by moving in contact with the sheet, and a contact force changing portion that changes a contact force with which the contact portion comes into contact with the sheet conveyed through the sheet conveyance path according to a type of the sheet conveyed through the sheet conveyance path.