JP2010102109A - Fixing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device for preventing the occurrence of paper wrinkles by securing an outer diameter difference between the end areas of at least one of a heating roller and a pressure roller and the central portion area thereof, and to provide an image forming apparatus with the fixing device. <P>SOLUTION: A control unit 210 sets a first target set temperature and a second target set temperature (S100) and starts energization of a main heater 200 and a sub-heater 201 (S110). Further, the control unit 210 determines whether the temperature of the central portion area is converged to the first target set temperature 310 (S140), and when determined that the temperature of the central portion area is converged to the first target set temperature (step S140;Yes), the control unit changes a target set value to the final target set temperature 300, to continue temperature control and perform convergence to the target set value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine and a printer, and a fixing device used in the image forming apparatus.

  In general, in a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, a fixing heating rotating body (heating roller) and a fixing heater that are pressed against each other to form a fixing nip portion. A pressure rotator (pressure roller) is provided, and the unfixed developer on the sheet (printing paper) is referenced to the center position in the axial direction of each roller with respect to the nip portion between the heating roller and the pressure roller. The paper is passed and fixed.

  Usually, in the fixing device, since the transfer material conveyance speed in the longitudinal direction at the nip portion is non-uniform, there is a problem that wrinkles that extend along the transfer material conveyance direction tend to occur at the central portion in the width direction of the transfer material. .

  Therefore, conventionally, by making the diameter of at least one end region of the heating roller and the pressure roller larger than the diameter of the central region, a difference in outer diameter between the end region and the central region is ensured. Take a way to prevent paper wrinkles.

  For this reason, at least one of the heating roller and the pressure roller of the fixing device has a pressure contact force distribution in the longitudinal direction in the fixing nip portion. The end region where the end edge is located has an outer shape such that the pressure contact force decreases toward the outside (see Patent Document 1). For example, it is preferable to have an outer diameter shape in which the central region has an inverted crown shape and the end region has a straight shape.

  Incidentally, a heater lamp having two coiled filaments is provided inside the heating roller of the fixing device. The first heater lamp has a heat generation width almost the same as the sheet passing width of the small-size sheet, and heats the central area. The other heater lamp heats only the end area and increases the large area. When the size sheet passes, the large size sheet is heated in cooperation with the first heater lamp. The fixing temperature is controlled by ON / OFF control of the two heater lamps.

  FIG. 5 is a diagram showing the control of the heating roller surface temperature by two conventional heater lamps.

  430 is a graph showing a temperature rise at the time of rising of the heating roller central region, and 420 is a graph showing a temperature rise at the time of rising of the heating roller end region. Reference numeral 400 denotes a target set temperature for the central region and the end region of the heating roller, and 410 denotes a temperature at which the heating roller starts to rotate. Further, 440 is an overshoot amount with respect to the target set temperature 400 in the central region.

  As shown in FIG. 5, the heating roller starts to rotate when the roller rotation start temperature 410 is reached, and the fixing roller is secured by raising the temperature of the pressure roller.

  Here, conventionally, the target set temperature 400 is set to the same temperature in the central region and the end region, or the target set temperature 400 in the central region is set higher than that in the end region.

In many cases, the time constant of the temperature rise in the central region is smaller than the time constant of the temperature rise in the end region, so that the central region reaches the target temperature sooner and the end region reaches the target temperature later. There are many cases to do.
JP 2005-352297 A

  However, due to the overshoot amount 440 in the central region, the temperature of the central region becomes higher than the temperature of the end region as shown in FIGS. In some cases, the diameter of the central region becomes larger than the initial set value than the diameter of the end region, and the inverted crown shape 510 becomes the normal crown shape 500.

  In this way, if the diameter of the central area becomes larger than the diameter of the edge area, if the paper is passed after reaching the target temperature, the difference in outer diameter between the edge area and the central area cannot be secured. There was a problem of my own occurrence.

  Therefore, in view of such circumstances, the present invention secures a difference in the outer diameter between the end region and the central region of at least one of the heating / pressure rollers, and a fixing device that prevents the occurrence of paper wrinkles. An image forming apparatus is provided.

  In order to solve the above-described problems, the present invention is configured as follows and has the following characteristics.

  According to a first aspect of the present invention, there is provided a fixing device including a heating roller and a pressure roller for fixing an unfixed developer on a sheet, wherein a central region of at least one of the heating roller and the pressure roller is provided. A first heater for heating, a first temperature detector for detecting the temperature of the first heater, and end regions at both ends in the longitudinal direction of at least one of the heating roller and the pressure roller are heated. A second target temperature for detecting the temperature of the second heater, a second temperature detector for detecting the temperature of the second heater, and a second target set temperature for the second heater. A controller configured to set the temperature of the first heater to a first target set temperature based on a temperature measured by the first temperature detector. To reach And controlling energizing said first heater.

  In the second aspect of the invention, the first target set temperature for the first heater and the second target set temperature for the second heater are the first temperature detection at the start of heating immediately after the power is turned on. And a temperature set based on the temperature measured by the second temperature detector.

  In the third aspect of the invention, the control unit further changes the first target set temperature to the second target set temperature after reaching the first target set temperature for the first heater. And controlling to reach the second target set temperature.

  In a fourth aspect of the invention, the first heater and the second heater are provided in parallel in a longitudinal direction in at least one of the heating roller and the pressure roller.

  In a fifth aspect of the invention, the first temperature detector and the second temperature detector are each provided at a surface position of the roller.

  A sixth aspect of the invention is characterized by comprising the fixing device according to any of the first to fifth aspects of the invention.

  According to the fixing device according to the present invention configured as described above and the image forming apparatus including the fixing device, the following excellent effects can be obtained.

  According to the present invention, by using thermal expansion, the diameter of the end region of at least one of the heating roller and the pressure roller is made larger than the diameter of the central region, thereby generating paper wrinkles. Can be prevented.

  Also, in order to set and control a target set temperature for each of the first and second heaters according to the surface temperature of at least one of the heating roller and the pressure roller at the time of warm-up startup, It is possible to prevent wrinkling of the paper immediately after the up.

  Further, after the detected temperature of the first heater reaches the target set temperature for the first heater, the setting is changed to the target set temperature set for the second heater, which is higher than the target set temperature. Further, by controlling so as to reach the target set temperature, it becomes possible to secure more fixability.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 to 4 are diagrams showing an example of an embodiment of a fixing device according to the present invention and an image forming apparatus provided with the fixing device. In the drawings, parts denoted by the same reference numerals as those in FIG. .
<Description of Overall Configuration and Outline Operation of Image Forming Apparatus>
FIG. 1 is a schematic configuration diagram showing the overall configuration of the image forming apparatus according to the present embodiment.

  The image forming apparatus 1 is a multifunctional multifunction apparatus in which a scanner 3, an automatic document conveying device 4, a sheet post-processing device 5, a multistage sheet feeding unit 6, and a relay conveying unit 8 are installed around a printer 2. The scanner 3 is supported on the system rack 7 together with the automatic document feeder 4 disposed on the upper portion thereof, and is disposed above the printer 2 and the sheet post-processing device 5.

  The printer 2 records and outputs the image data read from the image processing apparatus in an externally connected device such as a personal computer as well as recording and outputting the image read by the scanner 3. In the printer 2, an electrophotographic process unit 20 is arranged on the substantially right side of the center of the apparatus main body. A sheet supply unit 21 is disposed below the printer 2. The sheet supply unit 21 includes a sheet storage tray 210 that stores sheets and a separation supply unit 211 that separates and supplies the sheets stored in the sheet storage tray 210 one by one. The sheets supplied one by one from the sheet supply unit 21 are sequentially supplied between the photoconductor of the electrophotographic process unit 20 and the transfer unit, and the developed image is transferred from the photoconductor.

  Note that a sheet sent from the multi-stage sheet feeding unit 6 or the like prepared as a peripheral device is received below the sheet supply unit 21 and is directed between the photoconductor of the electrophotographic process unit 20 and the transfer unit. A sheet receiving port 27 for sequentially supplying the sheet is provided.

  A fixing device 23 is disposed above the electrophotographic process unit 20, and sequentially receives the sheets on which the images are transferred, heats and fixes the developer on the sheets, and sends the sheets out of the fixing device 23. The sheet on which the image is recorded is delivered from the discharge roller 28 of the printer 2 to the relay conveyance unit 8 on the upper side of the printer 2 body.

  As shown in FIG. 1, a process control unit (PCU) substrate 25 for controlling the electrophotographic process is provided in a space around the optical scanning unit 22, and an interface substrate for receiving image data from the outside of the apparatus, and this The image data received from the interface board and the image data read by the scanner 3 are subjected to predetermined image processing, and an image control unit (ICU) board for scanning the photoconductor by the optical scanning unit 22 is accommodated. A printer control unit 24, a power supply unit 26 for supplying power to these various substrates and units, and the like are arranged.

  The multi-stage sheet feeding unit 6 is an external sheet feeding device, and separates the sheets stored in the sheet storage tray 610 one by one by the separation feeding unit 611 and is provided on the upper surface of the unit to be a sheet of the printer 2. The sheet is supplied toward the sheet discharge port 62 communicating with the receiving port 27. In the present embodiment, the sheet supply unit 61 is stacked in three stages. During operation, the sheet supply unit 61 that accommodates a desired sheet selectively operates. Sheets are supplied to the sheet supply unit 61 by pulling out the sheet storage tray 610 to the front side of the unit main body.

  Further, the multi-stage paper feeding unit 6 is configured to place the printer 2 and the post-processing device 5 on the upper part, but moves in this state so that it can be fixedly installed between the system racks 7. The moving roller 63 and the fixed part 64 are provided at the lower part. At the time of movement, the fixing portion 64 is rotated and raised to separate the fixing portion 64 from the floor surface. At the time of fixing, the fixing portion 64 is rotated and lowered to bring the fixing portion 64 into contact with the floor surface. The paper feed unit 6 is fixed.

  The sheet post-processing device 5 performs post-processing on the sheet by guiding a sheet on which an image discharged from the relay conveyance unit 8 and the printer 2 is recorded at the upper portion of the device with a carry-in roller 50.

  Post-processing includes stapling, sorting, and the like. The apparatus illustrated here has a configuration including three paper discharge trays 51. If necessary, sheets can be fed by gates 52 and 53. The sheet is discharged by switching the discharge tray 51 to be discharged. For example, the upper discharge tray 51a is used for discharging sheets in the copy mode, the interrupted discharge tray 51b is used for discharging sheets in the print mode, and the lower discharge tray 51c is discharged in the facsimile print mode. For example, it can be discharged according to its use.

  The scanner 3 automatically supplies a sheet-like document by the automatic document conveying device 4 and sequentially exposes and scans the images one by one to read a document image and a book-like document or the automatic document conveying device 4. A manual reading mode for reading a document image by setting a sheet-like document that cannot be automatically supplied by manual operation is provided. Then, the image of the document set on the transparent document placing table 30 is exposed and scanned by the first scanning unit 31 and the second scanning unit 32 that move along the document placing table 30 with a predetermined speed relationship with each other. The original image is converted into an electrical signal and output by being guided by an optical component such as a mirror or an imaging lens 33 and forming an image on the photoelectric conversion element 34.

  The automatic document conveying device 4 includes a document conveying means 41 that conveys a document placed on the document setting tray 40 toward the document placing table 30 and discharges the scanned document onto a document discharge tray 42. Yes. In addition, the front side of the apparatus is opened so that a sheet document that cannot be automatically supplied can be placed on the document placement table 30 and scanned so that it can be scanned. It is configured.

  The relay conveyance unit 8 is mounted on an upper portion of a paper discharge tray 29 provided at the top of the printer 2, and a sheet post-processing device 5 positioned on the downstream side of the printer 2 is used to record a sheet on which an image has been discharged from the printer 2. It is the conveyance unit for introducing toward.

Further, in the middle of the sheet conveyance path 84 of the relay conveyance unit 8, another sheet conveyance path 83 for guiding the sheet to the discharge tray 9 formed by the upper surface 82 of the unit and the upper surface 54 of the sheet post-processing apparatus 5. However, it is branched. The two discharge destinations can be changed by switching the gate 81 arranged at the branch portion of the transport path.
<Description of Specific Configuration of Fixing Device>
FIG. 2 is a block diagram showing an electrical control system of a heater lamp provided inside the heating roller of the fixing device according to the present embodiment.

  The fixing device 23 according to the present embodiment includes a heating roller that fixes an unfixed developer on a sheet (printing paper), a pressure roller, and a control unit 210 that controls the entire fixing device. In the heating roller, a first heater lamp (main heater) 200 having a coiled filament having substantially the same width as that of a small size sheet and a width of the large size sheet are substantially the same. Two types of heater lamps, a second heater lamp (sub-heater) 201 provided with a coiled filament having a width, are provided.

  Each of the filaments of each heater lamp has a heat generating portion and a non-heat generating portion. The filament heat generating portion 202 in the main heater 200 is disposed so as to face the filament non-heat generating portion 203 in the sub heater 201. That is, the heating roller includes a main heater 200 that distributes heat in the axial center region, and a sub-heater 201 that distributes heat in the left and right axial regions and does not distribute heat in the axial center region.

  As shown in FIG. 2, temperature detectors (temperature sensors) 204 and 205 are installed within the heat generation width of the main heater 200 and the sub heater 201, and signals detected by these temperature sensors are input to the input circuit 206. , 207, and taken into the control unit (hereinafter referred to as CPU) 210.

  The CPU 210 performs energization control of the main heater 200 and the sub heater 201 via the drivers 208 and 209 based on the heating roller surface temperature detected by these temperature sensors, and performs control processing so as to reach the target set temperature.

The power consumption of the main heater 200 and the sub heater 201 is, for example, 600 W.
<Description of Specific Operation of Fixing Device>
FIG. 3 is a graph showing rising characteristics of the surface temperature of the heating roller of the fixing device 23 according to the present embodiment.

  As shown in FIG. 3, the method for controlling the surface temperature of the heating roller of the fixing device 23 according to the present embodiment is such that the rising temperature characteristic (330) of the end region of the heating roller is the rising temperature characteristic (340) of the central region. Since it is moderate in comparison and the amount of overshoot is small, the surface temperature of the end area of the heating roller is directly controlled to reach the final target set temperature (referred to as the second target set temperature). .

  On the other hand, in the control of the surface temperature of the central region of the heating roller, since the rising temperature characteristic is steep and the amount of overshoot is large, the second target temperature that is the final target set temperature of the surface temperature of the end region of the heating roller is the second. A first target set temperature set lower than the target set temperature is provided, and the first target set temperature is temporarily reached from the time of warm-up rising (at the time of rising from the case where the current temperature is below α ° C.). Then, control is performed so as to reach the second target set temperature, which is the final target set temperature.

  By doing this, the amount of overshoot (360) at the surface temperature of the central region at the time of start-up is reduced, the central region is prevented from becoming hotter than the end region, and the roller diameter of the central region is expanded. It is possible to prevent the roller diameter in the end region from becoming larger than the expansion. Therefore, the reverse crown shape 500 shown in FIG. 6A does not occur, and the generation of “wrinkles” can be avoided.

  When the warm-up time of the heating roller is long, the pressure roller is supplied with a large amount of heat from the heating roller, so that the amount of change in expansion of the roller diameter increases.

  Therefore, the second target set temperature needs to be set lower than when the warm-up time is short.

  In this case, if there is a large difference of 15 ° C. or more between the first target set temperature and the second target set temperature, it is also necessary to provide a third target set temperature and control it in two stages. is there.

  Next, processing of the surface temperature control operation of the heating roller will be described with reference to an operation flowchart shown in FIG.

  First, the CPU 210 sets a first target set temperature and a second target set temperature, which are final target set temperature values (step S100), and starts energization of the main heater 200 and the sub heater 201 (step S110). It is determined whether the temperature measured by the temperature sensor 204 has reached the heating roller rotation temperature (step S120). If the temperature has been reached (step S120; Yes), rotation of the roller is started (step S130). If not reached (step S120; No), the temperature measurement is continued, and the process returns to step S120.

  Further, the CPU 210 determines whether or not the temperature in the central region has converged to the first target set temperature 310 (step S140). If it is determined that the temperature has converged (step S140; Yes), the final target set temperature ( The target set value is changed to (second target set temperature) 300, temperature control is continued, and the target set value is converged. At the time of convergence, a printable instruction is output and this process is terminated (step S150). If it has not converged (step S140; No), the process returns to step S140, and the process is repeated until it converges.

  Note that the fixing device of the present invention and the image forming apparatus using the same are not limited to the above-described illustrated examples, and can be variously modified without departing from the scope of the present invention. .

1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus according to an exemplary embodiment. FIG. 3 is a block diagram illustrating a configuration of an electrical control system of a heater lamp provided inside a heating roller of the fixing device according to the present embodiment. 6 is a graph showing the rising characteristics of the surface temperature of the heating roller of the fixing device according to the present embodiment. It is a figure which shows the operation | movement flow of rising temperature control of a heating roller. It is a figure which showed control of the heating roller surface temperature by the heater lamp of the conventional fixing device. It is a figure which shows the shape in the temperature rise (at the time of starting) of a heating roller, (a) is a figure which shows the normal crown shape of a heating roller, (b) is a figure which shows the reverse crown shape of a heating roller. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Printer 3 Scanner 4 Automatic document conveying apparatus 5 Sheet post-processing apparatus 6 Multi-stage sheet feeding unit 7 System rack 8 Relay conveying unit 23 Fixing apparatus 200 First heater lamp 201 Second heater lamp 202 Heating section 203 Heat generating section 204, 205 Temperature sensor 206, 207 Input circuit 208, 209 Driver 210 Control section 330, 420 Rising temperature characteristics 340, 430 at the end area 360 Rising temperature characteristics at the center area 360, 440 Overshoot amount 500 Reverse crown shape 510 Regular crown shape

Claims (6)

A fixing device including a heating roller and a pressure roller for fixing an unfixed developer on a sheet,
A first heater for heating a central region of at least one of the heating roller and the pressure roller;
A first temperature detector for detecting the temperature of the first heater;
A second heater for heating end regions at both ends in the longitudinal direction of at least one of the heating roller and the pressure roller;
A second temperature detector for detecting the temperature of the second heater;
A controller configured to set a first target set temperature for the first heater to be lower than a second target set temperature for the second heater;
The controller controls the first heater so as to reach the first target set temperature from the temperature at the start of heating of the first heater based on the temperature measured by the first temperature detector. A fixing device characterized by being energized and controlled.   The first target set temperature for the first heater and the second target set temperature for the second heater are the first temperature detector and the second temperature at the start of heating immediately after the power is turned on. The fixing device according to claim 1, wherein the fixing device is set based on a temperature measured by a detector.   The controller further changes the setting of the first target set temperature to the second target set temperature after reaching the first target set temperature for the first heater, and sets the second target set temperature. The fixing device according to claim 1, wherein the fixing device is controlled to reach a temperature.   4. The device according to claim 1, wherein the first heater and the second heater are provided in parallel in a longitudinal direction in at least one of the heating roller and the pressure roller. The fixing device according to claim 1.   5. The fixing device according to claim 1, wherein the first temperature detector and the second temperature detector are respectively provided on a surface position of the roller. 6. .   An image forming apparatus comprising the fixing device according to claim 1.

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