JP2003149983A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent increases in the temperatures of the ends of a heater by detecting the size of paper that is smaller in width than specified paper. SOLUTION: In an image forming device having a fixing unit in which thermisters are disposed in the middle and ends of the heater, an engine informs a controller of mismatch of paper size when paper size information and increases in the temperatures of the thermisters do not match.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus in which a fixing device having a thermistor disposed at each of a central portion and an end portion of a heater is mounted. 2. Description of the Related Art In an image forming apparatus such as a copying machine, a facsimile machine, a laser printer, etc., a toner image (unfixed image) formed on a sheet (printing paper) is heated and pressed onto the paper. A fixing device (fixing device) for fixing is provided. The power consumed by this fixing device occupies the majority of the device, and even during standby when printing is not yet performed, the fixing device is often preheated. Device. Therefore, in recent years, an on-demand type fixing device which has a high heating efficiency for paper and has a small heat capacity has been put to practical use. The on-demand type fixing device will be described with reference to FIG. In FIG. 3, reference numeral 301 denotes a heating film, 302 denotes a plastic film guide,
03 is a thermistor, 304 is a heater (heating element)
305 is a ceramic base, 306 is a metal core, 307 is a pressure roller, and 308 is a paper discharge transport roller. The heater 304 is printed and fired on the surface of the ceramic base 305, and the thermistor 303 is bonded to the surface of the ceramic base 305 opposite to the heater 304. The plastic film guide 302 and the ceramic base 305 are mutually pulled by a spring with a desired force. As a result, the pressure roller 307 made of an elastic material and the heating film 301 come into contact with a predetermined nip width. A controller for controlling the fixing device shown in FIG. 1 reads the temperature of the thermistor 303 and sets the heater 30 so that the temperature of the thermistor 303 becomes a desired value.
4 is controlled. The core metal 306 is the core metal 30
6, the core metal 306 and the pressure roller 307 rotate in the direction of arrow A in the figure. Then, the heating film 301 is
07, the pressure roller 307 rotates in the direction of arrow B. The sheet on which the toner image (unfixed image) is formed is conveyed in the direction of arrow C in the figure and enters the nip between the heating film 301 and the pressure roller 307. Then, the heat generated by the heater 304 is transmitted to the heating film 301, and further heats the paper entering the nip. [0005] In this way, heat and pressure are applied to the sheet that has entered the nip, and the toner image formed on the surface is melted and fixed on the sheet surface. Thereafter, the sheet on which the toner image has been fixed is discharged to the outside of the fixing device by a sheet discharge conveyance roller. The feature of the on-demand type fixing device is that the temperature in the fixing section can be rapidly raised from room temperature to the fixing temperature. This is because the heat capacity of the ceramic base 305 and the heating film 301 is small, and the distance between the heater 304 and the fixing nip can be shortened. Further, since the plastic film guide 302 and the pressure roller 307 are basically made of plastic, the heat resistance thereof can be increased, and the heat generated by the heater 304 is hardly transmitted to the plastic film guide 302 and the pressure roller 307. . As described above, the heat generated by the heater 304 can be transmitted to the sheet with high efficiency. [0007] Since rapid heating can be performed as described above, it is possible to interrupt heating of the heater when the printing apparatus is on standby and to heat only during printing. This is an advantage that cannot be achieved by a fixing device using another halogen lamp that requires preheating. In the fixing device described above, since rapid heating is performed, continuous printing is performed on paper having a width smaller than the width of the heater, such as a postcard or an envelope. The temperature of the end of the heater rises so that heat is not deprived by the sheet. If the fixing device is continuously used in a state where the temperature of the end portion is raised, an excessive thermal stress is applied to the fixing device, which affects the image quality. In the conventional apparatus, when printing on paper having a width smaller than the width of the heater, such as a postcard or an envelope, for example, the end portions are not excessively heated by providing a printing interval in advance. Was like that. Therefore, in order to increase the throughput as much as possible, a thermistor is provided at the end of the heater, and control is performed such that a printing interval is provided only when the temperature of the end of the heater rises. However, when a sheet width different from the sheet size set by the host computer, for example, a sheet length of A4 size and a sheet width of B5 size is set, a new sheet width detection sensor is required. According to the present invention, in an image forming apparatus equipped with a fixing device in which a thermistor is disposed at each of a central portion and an end portion of a heater, if the temperature rises of the thermistors do not match, the host computer generates a misprint An object of the present invention is to provide an image forming apparatus characterized in that printing is not performed continuously by notifying. [0012] The present invention can solve the above-mentioned problems by providing the following constitution. (1) It has a heating element, and has means for detecting the temperature at the center and the end of the heating element. By controlling the temperature, a control is performed to keep the temperature constant, and the toner on the recording paper is removed. In an image forming apparatus having a fixing mechanism, when the relationship between the temperature change of the temperature detecting means at the center and the temperature change of the temperature detecting means at the end of the heating element corresponding to the paper size set in advance does not match, the host computer is notified. On the other hand, an image forming apparatus having means for notifying a mismatch of paper sizes. (First Embodiment) FIG. 1 is a block diagram of a printer system including a printer controller and a printer engine according to a first embodiment of the present invention. Reference numeral 101 denotes a display, and 102 denotes a host.
It is a computer. A printer controller 103 converts the image data transmitted from the computer 102 into an image signal so that raster scanning can be performed, and controls a printer engine 104 through an interface. Controller 103 and engine 10
4 are both contained in the same printer fluid. The components in the controller 103 are as follows. 103a: a display unit on the surface of the printer housing. 103b: an operation unit on the surface of the printer housing. 103c: controller CPU. 103d: ROM in CPU 103c. 103e: RAM in CPU 103c. FIG. 2 is a mechanical configuration diagram of the engine of the first embodiment. The printer comprises a main body 201 and an optional paper feeder 202 as an option. Reference numeral 203 denotes a front cover.
MPT (Multi-Purp) which is a manual paper feed tray
ose Ray) 204 can be used. 205 is MP
This is a flag of a sensor that detects the presence of a sheet on T. 20
Reference numeral 6 denotes an MPT paper feed roller for conveying the paper on the MPT 204 into the printer. Reference numeral 207 denotes a PCT (Pap) which is a standard paper feeding unit.
er Cassette Tray). Reference numeral 208 denotes a sensor flag for detecting the presence of a sheet on the PCT.
Reference numeral 209 denotes a PCT paper feed roller for conveying the paper on the PCT 207 to the inside of the printer. An optional paper feed unit OPT 210 is provided.
(Optional Paper Cassette
(Tray). Reference numeral 211 denotes a sensor flag for detecting the presence of a sheet on the OPT. Reference numeral 212 denotes an OPT paper feed roller for conveying the paper on the OPT 210 to the inside of the printer. Reference numeral 213 denotes a roller for further conveying the paper fed from the PCT and OPT to the inside of the printer. The transport direction of the paper fed from any of MPT, PCT, and OPT is corrected by temporarily abutting the leading end of the paper on the registration shutter 214, and when a predetermined transport force is applied, the paper is further advanced. The sheet is conveyed by reaching the conveying roller 215. Immediately after the conveyance roller 215, there is a sensor flag 216 called a TOP sensor, which synchronizes the image of the sheet conveyed with the image. Reference numeral 217 denotes a known toner cartridge. A primary charging roller 218, a photosensitive drum 219, and a developing cylinder 220 are provided inside. 221 is a transfer roller. To write the electrostatic latent image, a predetermined laser beam is applied to a polygon mirror 224 rotated and driven by a motor 223 in the scanner unit 222.
By irradiating the photosensitive drum 219 with the folding mirror 225. After the paper passes the toner transfer position, the fixing belt 227 and the pressing roller 2
28, where the toner image is fixed on the paper. A paper discharge sensor 229 detects the presence of paper immediately after the fixing device. The sheet that has passed through the fixing device is further conveyed by a sheet discharging roller 230. Face Up Tray 2
When the sheet 31 is open as shown in the figure, the sheets are stacked on the tray 231. When the tray 231 is closed, the prepared paper reaches the rollers 232 and is stacked on the face-down tray 233. Reference numeral 234 denotes an upper door. When the upper door is opened upward, the toner cartridge 217 can be taken in and out. FIG. 4 shows the arrangement of the thermistors of the on-demand type fixing device shown in FIG. The thermistor 401 is disposed at the center of the heater 304, and the thermistor 402 is disposed at an end of the heater 304. The thermistor 402 has an area 403 through which normal wide-size paper passes.
In the range 404 where the paper passes and where the narrow-sized paper passes, it is located at a position deviated from the position where the paper passes. During normal printing, the temperature control of the heater 304 is controlled so as to be constant based on the temperature detected by the thermistor 401. FIG. 5 shows the temperature change at that time. After the power is turned on, after a lapse of time 501, the temperature control is performed so that the temperature becomes constant at the temperature 502. At this time, when printing on a wide-size sheet, the thermistor 402 performs the same temperature change as the thermistor 401. On the other hand, when printing on paper of a narrow width, the temperature of the thermistor 402 rises by the temperature 504 as compared with the temperature of the thermistor 401 after a predetermined time 503. If the paper size instruction at the time of printing is a narrow paper, printing is continued as it is. However, if a wide-size paper size is designated, it is reported to the host computer as a misprint due to paper size mismatch. As described above, according to the first aspect of the present invention, the thermistors disposed at the center and the end of the heater serve as a misprint due to a paper size mismatch to the host computer. Since the notification is made, the paper width size can be detected without newly providing a paper width detection sensor, and continuous printing is not performed by notifying a misprint, so that the temperature rise at the end of the heater is prevented. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric block diagram of a laser printer used in the present invention. FIG. 2 is a schematic view of a laser printer used in the present invention. FIG. 3 is an on-demand type fixing device used in the present invention. FIG. 4 is a schematic view of the arrangement of a thermistor of a fixing device used in the present invention. FIG. 5 is a temperature change diagram of a thermistor used in the present invention. [Description of Signs] 201 Laser printer body 301 Heating film 304 Heater 401 Thermistor 402 Thermistor

Claims (1)

Claims: 1. A heating element, comprising means for detecting the temperature of the central part and the end part of the heating element, and controlling to keep the temperature constant while detecting the temperature. In an image forming apparatus having a mechanism for fixing toner on recording paper, the relationship between the temperature change of the temperature detecting means at the center and the temperature change of the temperature detecting means at the end of the heating element corresponding to a preset paper size does not match. Sometimes, an image forming apparatus having means for notifying a host computer of a paper size mismatch.