US-20260126749-A1 - IMAGE FORMING APPARATUS THAT CONTROLS SHEET INTERVAL

US20260126749A1US 20260126749 A1US20260126749 A1US 20260126749A1US-20260126749-A1

Abstract

An image forming apparatus includes a conveyance member to convey a sheet, an image forming unit, a fixing device, a component, and a controller. The image forming unit forms a toner image on the conveyed sheet conveyed. The fixing device fixes an unfixed toner image formed on the sheet, onto the sheet. Heat of the fixing device propagates to the component. The controller controls a passing sheet interval between a plurality of sheets passing through the fixing device. The controller executes throughput control for controlling a sheet interval, which is an interval between a preceding sheet and a subsequent sheet passing through the fixing device, such that a temperature of a non-passage region through which sheets do not pass in the fixing device is suppressed to a predetermined first limit temperature or less and a temperature of the component is suppressed to a predetermined second limit temperature or less.

Inventors

Hiromitsu Takano
Takanori Mitani
Satoru Nagashima
Takeshi Shimba

Assignees

CANON KABUSHIKI KAISHA

Dates

Publication Date: 20260507
Application Date: 20251231
Priority Date: 20230410

Claims (1)

1 . An image forming apparatus comprising: a conveyance member configured to convey a sheet; an image forming unit configured to form a toner image on the sheet conveyed by the conveyance member; a fixing device configured to fix an unfixed toner image formed on the sheet, onto the sheet; a component to which heat of the fixing device propagates; and a controller configured to control a passing sheet interval between a plurality of sheets passing through the fixing device, wherein the controller is configured to execute throughput control for controlling a sheet interval, which is an interval between a preceding sheet and a subsequent sheet passing through the fixing device, such that a temperature of a non-passage region through which sheets do not pass in the fixing device is suppressed to a predetermined first limit temperature or less and a temperature of the component is suppressed to a predetermined second limit temperature or less.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation of U.S. Patent Application No. 18/628,530, filed on April 5, 2024, which claims priority from Japanese Patent Application No. 2023-063617, filed April 10, 2023, each of which is hereby incorporated by reference herein in their entireties. BACKGROUND FIELD The present disclosure relates to image forming apparatus that controls sheet interval. Description of the Related Art A fixing device that fixes a toner image on a sheet using an electrophotographic process fixes the toner image onto the sheet by applying heat to the sheet and the toner image. The width (length in a direction perpendicular to a sheet conveying direction) of the fixing device is designed such that a sheet of a maximum size envisioned can pass through the fixing device. Accordingly, when a sheet smaller than the maximum size passes through the fixing device, the temperature of a region (non-passage region) where the sheet does not pass in the fixing device increases. This is because heat is not taken away by the sheet in the non-passage region. If the temperature of the non-passage region becomes too high, a support member that supports a heater of the fixing device and the like will be affected by the heat. In view of this, according to Japanese Patent Laid-Open No. H06-149103, it is proposed that an excessive temperature rise in a non-passage region is suppressed by providing an interval between a plurality of sheets that are to pass through a fixing device. This is called throughput-down control. The term “throughput” refers to the number of sheets processed per unit time. Incidentally, a sheet sensor for detecting a jam is arranged outside the fixing device in some cases. In this case, it is necessary to protect the sheet sensor from the heat emitted from the fixing device. SUMMARY According to an aspect of the present disclosure, an image forming apparatus includes a conveyance member configured to convey a sheet, an image forming unit configured to form a toner image on the sheet conveyed by the conveyance member, a fixing device configured to fix an unfixed toner image formed on the sheet, onto the sheet, a component to which heat of the fixing device propagates, and a controller configured to control a passing sheet interval between a plurality of sheets passing through the fixing device, wherein the controller is configured to execute throughput control for controlling a sheet interval, which is an interval between a preceding sheet and a subsequent sheet passing through the fixing device, such that a temperature of a non-passage region through which sheets do not pass in the fixing device is suppressed to a predetermined first limit temperature or less and a temperature of the component is suppressed to a predetermined second limit temperature or less. Further features of the present disclosure will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating an image forming apparatus FIG. 2 is a block diagram illustrating a controller. FIG. 3 is a diagram illustrating a fixing device. FIGS. 4A and 4B are diagrams illustrating a heater. FIG. 5 is a diagram illustrating the heater, width sensors, and a sheet passage region. FIG. 6 is a diagram illustrating throughput control. FIG. 7 is a diagram illustrating throughput control. FIG. 8 is a diagram illustrating functions of a CPU. FIG. 9 is a flowchart showing a method for determining a sheet interval. FIG. 10 is a diagram illustrating a method for increasing a sheet interval. FIG. 11 is a diagram illustrating functions of the CPU. FIG. 12 is a flowchart showing a method for determining a sheet interval. DESCRIPTION OF THE EMBODIMENTS Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the disclosure. Multiple features are described in the embodiments, but limitation is not made that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted. Embodiment 1 (1) Structure of Image Forming Apparatus FIG. 1 shows an image forming apparatus 100 that forms full-color images using four stations. A first station forms a yellow “Y” toner image. A second station forms a magenta “M” toner image. A third station forms a cyan “C” toner image. A fourth station forms a black “K” toner image. Note that a, b, c, and d, which are added to the ends of reference numerals, indicate yellow, magenta, cyan, and black, respectively. In this specification, when an item that is the same for the four colors is described, the letters a, b, c, and d are omitted from the reference numeral. A process cartridge 9 is pro