JP2017181833A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of suppressing undershooting and overshooting caused when fixation processing of different sheet size is continuously performed without setting a standby state.SOLUTION: An image formation apparatus comprises: a plurality of halogen lamp heaters 187-189 of different light distribution for heating a fixing roller 183 of an image fixation part 18 for fixing toner on a recording medium by heating and pressing the recording medium to which the toner is transferred; a temperature detection part 186 which measures a surface temperature of the fixing roller 183; a changeover detection part which detects a changeover from a first recording medium to a second recording medium different in width, perpendicular to a conveyance direction, from the first recording medium; and a control part which determines a heating pattern for the second recording medium based upon the measured temperature of the temperature detection part 186 and a detection result of the changeover detection part, and starts controlling the halogen lamp heaters 187-189 with the heating pattern at timing a predetermined number retroactive from the first recording medium to be subjected to fixation processing lastly.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus.

  Conventionally, in the fixing control of an image forming apparatus, when the size of a sheet as a recording medium, in particular, the width in the direction perpendicular to the transport direction changes, a temporary standby state (for example, an idling state) is entered and the fixing is performed. By fixing and stabilizing the surface temperature of the non-sheet passing end portion of the fixing member such as a roller or a pressure roller, the fixing quality and the stability of paper conveyance are maintained.

  In such a standby period, of course, fixing processing is not performed, which is a problem in an image forming apparatus that places importance on productivity. For this reason, an image forming apparatus that places emphasis on productivity uses an image forming method in which fixing processing of different paper sizes is continuously performed without entering a standby state at the timing when the size of the recording medium is changed.

  However, when an image forming method that emphasizes productivity is used, there is no standby state for recovering and stabilizing the surface temperature of the non-sheet passing end portion of the fixing member, so that the surface temperature of the end portion of the fixing member undershoots. As a result, there arises a problem that the fixing quality is deteriorated or the stability of sheet conveyance is deteriorated due to overshoot.

  In order to prevent deterioration of the fixing quality due to such undershoot or overshoot of the surface temperature of the end portion of the fixing member, the heating portions of two different light distributions according to the width in the direction perpendicular to the paper transport direction. An image forming apparatus that stabilizes the surface temperature of the fixing member by changing the lighting rate (see Patent Document 1), or an image forming apparatus that performs appropriate temperature control without undershoot or overshoot when the paper size is switched ( Patent Document 2) is known.

Japanese Patent Laying-Open No. 2015-007716 JP 2013-148721 A

  However, in the image forming apparatus described in Patent Document 1, although the lighting ratios of the heating units of two different light distributions are changed according to the width in the direction perpendicular to the sheet conveyance direction, the standby and printing operations are performed. The lighting rate is also changed, and a standby state is required.

  The image forming apparatus described in Patent Document 2 performs appropriate temperature control without undershoot or overshoot, but also performs temperature control in a standby state (warm-up). It becomes necessary.

  For this reason, there is a problem in that undershoot and overshoot that occur when fixing processes of different paper sizes are continuously performed without requiring a standby state cannot be suppressed.

  An object of the present invention is to provide an image forming apparatus capable of suppressing undershoot and overshoot that occur when fixing processing of different paper sizes is continuously performed without requiring a standby state.

In order to achieve the above object, an image forming apparatus according to claim 1 is provided.
A plurality of heating units with different light distributions for heating a fixing roller of an image fixing unit that heats and pressurizes the recording medium on which the toner is transferred to fix the toner to the recording medium;
A measuring unit for measuring the surface temperature of the fixing roller;
A detection unit for detecting switching from the first recording medium to a second recording medium having a width different from that of the first recording medium in a direction perpendicular to the conveyance direction;
A heating pattern for the second recording medium is determined based on the measurement temperature of the measurement unit and the detection result of the detection unit, and the timing is traced back by a predetermined retrospective number from the first recording medium to be fixed last. A control unit for starting control of the heating unit by a heating pattern;
It is characterized by having.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The control unit is characterized in that the heating pattern is determined based on a width in a direction perpendicular to a conveyance direction of the second recording medium.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
The plurality of heating units have a light distribution pattern that is parallel to the transport direction of the second recording medium and symmetrical with respect to a straight line passing through the center.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects,
Based on the detection result of the detection unit, the control unit sets one of the plurality of heating units having different light distributions as a main heating unit that mainly heats, and sets the other as a sub-heating unit that supplementarily heats the other. It is characterized by determining a heating pattern.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects,
The said control part determines the said heating pattern by ON / OFF control or HCD control, or these combination.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The detection unit detects switching of the second recording medium based on set job information or a selection state of a paper feed tray.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects,
The control unit determines the retroactive number based on at least one of a width of the recording medium, a basis weight of the recording medium, a number of sheets to be passed, or a combination thereof.

The invention according to claim 8 is the image forming apparatus according to any one of claims 1 to 7,
An external heating unit for heating the pressure roller of the image fixing unit;
When the width of the second recording medium is smaller than the width of the first recording medium, the control unit turns off the external heating unit at the timing when the recording medium is switched.

  According to the present invention, it is possible to suppress undershoot and overshoot that occur when fixing processing of different paper sizes is continuously performed without setting a standby state.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment to which the present invention is applied. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus. FIG. FIG. 3 is a schematic diagram illustrating a configuration of an image fixing unit. FIG. 2 is a schematic diagram illustrating an internal configuration of a fixing roller. 6 is a flowchart illustrating an example of an operation of the image forming apparatus. It is explanatory drawing which shows an example of a heating pattern. It is explanatory drawing which shows another example of a heating pattern. It is explanatory drawing which shows an example of the evaluation result of an Example and a comparative example. It is explanatory drawing which shows an example of the overshoot in an Example. It is explanatory drawing which shows an example of the overshoot in a comparative example. It is explanatory drawing which shows an example of the undershoot in an Example. It is explanatory drawing which shows an example of the undershoot in a comparative example. It is explanatory drawing which shows an example at the time of changing the switching timing of external heating in an Example.

(Embodiment)
[1. Description of configuration]
Hereinafter, an embodiment of the image forming apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus 1.

The image forming apparatus 1 includes a control unit 10 having a CPU 101 (Central Processing Unit), a RAM 102 (Random Access Memory), and a ROM 103 (Read Only Memory), a storage unit 11, an operation unit 12, a display unit 13, an interface 14, a scanner 15, An image processing unit 16, an image forming unit 17, an image fixing unit 18, a transport unit 19, a switching detection unit 20 and the like are provided. The control unit 10 includes a storage unit 11, an operation unit 12, a display unit 13, an interface 14, a scanner 15, an image processing unit 16, an image forming unit 17, an image fixing unit 18, a transport unit 19, and a switching detection unit via a bus 21. 20 is connected.

  The CPU 101 reads out and executes a control program stored in the ROM 103 or the storage unit 11 and performs various arithmetic processes.

  The RAM 102 provides a working memory space to the CPU 101 and stores temporary data.

  The ROM 103 stores various control programs executed by the CPU 101, setting data, and the like. Instead of the ROM 103, a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

  The control unit 10 including the CPU 101, the RAM 102, and the ROM 103 performs overall control of each unit of the image forming apparatus 1 according to the various control programs described above. For example, the control unit 10 causes the image processing unit 16 to perform predetermined image processing on the image data and store the image data in the storage unit 11. In addition, the control unit 10 causes the conveyance unit 19 to convey the sheet, and causes the image forming unit 17 to form an image on the sheet based on the image data stored in the storage unit 11.

  The storage unit 11 includes storage means such as a DRAM (Dynamic Random Access Memory) or HDD (Hard Disk Drive), which is a semiconductor memory, and is input from the outside through image data acquired by the scanner 15 or the interface 14. Stored image data and the like. These image data and the like may be stored in the RAM 102.

  The operation unit 12 includes an input device such as an operation key or a touch panel arranged on the screen of the display unit 13. The operation unit 12 converts an input operation on these input devices into an operation signal and outputs the operation signal to the control unit 10.

  The display unit 13 includes a display device such as an LCD (Liquid crystal display), and displays an operation screen and the like indicating the state of the image forming apparatus 1 and the content of an input operation to the touch panel.

  The interface 14 is a unit that transmits and receives data to and from an external computer, another image forming apparatus, and the like, and includes, for example, any of various serial interfaces.

  The scanner 15 reads an image formed on a sheet, generates image data including single-color image data for each of R (red), G (green), and B (blue) color components, and stores the image data in the storage unit 11.

  The image processing unit 16 includes, for example, a rasterization processing unit, a color conversion unit, a gradation correction unit, and a halftone processing unit. The image processing unit 16 performs various types of image processing on the image data stored in the storage unit 11 and stores the image data in the storage unit 11. .

  The image forming unit 17 forms an image on a sheet based on the image data stored in the storage unit 11. The image forming unit 17 includes four exposure units 171, a photoconductor 172, and a developing unit 173 that respectively correspond to color components of C (cyan), M (magenta), Y (yellow), and K (black). . Further, the image forming unit 17 includes a transfer body 174 and a secondary transfer roller 175.

The exposure unit 171 includes an LD (Laser Diode) as a light emitting element. Exposure unit 171
Drives the LD based on the image data, and irradiates and exposes the photosensitive member 172 to be charged with laser light to form an electrostatic latent image on the photosensitive member 172. The developing unit 173 supplies toner (coloring material) of a predetermined color (any of C, M, Y, and K) by a developing roller that is charged on the exposed photoconductor 172, and is formed on the photoconductor 172. The developed electrostatic latent image is developed.
Images (monochromatic images) formed with C, M, Y, and K toners on four photoconductors 172 corresponding to C, M, Y, and K are sequentially superimposed on the transfer member 174 from each photoconductor 172. To be transcribed. As a result, a color image having C, M, Y, and K as color components is formed on the transfer body 174. The transfer body 174 is an endless belt wound around a plurality of transfer body transport rollers, and rotates according to the rotation of each transfer body transport roller.
The secondary transfer roller 175 transfers the color image on the transfer body 174 onto a sheet fed from the sheet feeding tray 22 or a sheet feeding device provided outside. More specifically, when a predetermined transfer voltage is applied to the secondary transfer roller 175 that sandwiches the paper and the transfer body 174, the toner forming the color image on the transfer body 174 is attracted to the paper side and applied to the paper. Transcribed.

  The image fixing unit 18 performs a fixing process for fixing the toner onto the paper by heating and pressurizing the paper on which the toner has been transferred.

  FIG. 3 is a schematic diagram showing the configuration of the image fixing unit 18. The image fixing unit 18 includes a fixing roller 183, a pressure roller 184, an external heating roller 185, a temperature detection unit 186, and the like. The image fixing unit 18 and the control unit 10 constitute a fixing device.

  The fixing roller 183 includes halogen lamp heaters 187 to 189 which are fixing lamps (or fixing heaters) extending in the rotation axis direction. The halogen lamp heaters 187 to 189 generate heat when energized under the control of the control unit 10. The fixing roller 183 is driven to rotate by a rotation driving unit such as a motor (not shown) under the control of the control unit 10. The fixing roller 183 is provided with a temperature detection unit 186 that detects the temperature of the fixing roller 183. One temperature detector 186 or a plurality of temperature detectors 186 may be provided as long as the temperature of the fixing roller 183 can be detected.

  Further, the outer heating roller 185 includes an outer heater 190 that extends in the direction of the rotation axis. The external heater 190 generates heat when energized under the control of the control unit 10. Then, the external heating roller 185 contacts the pressure roller 184 and directly heats the pressure roller 184.

FIG. 4 is a schematic diagram illustrating an internal configuration of the fixing roller 183.
The halogen lamp heaters 187 to 189 include tungsten filaments 187b to 189b in the cylindrical portions 187a to 189a, respectively, and halogen gases of a predetermined concentration are sealed in the cylindrical portions 187a to 189a, respectively. Based on the concentration of the halogen gas sealed in the tube portions 187a to 189a, the reference voltages of the halogen lamp heaters 187 to 189 are set.

  Further, the filament 187b of the halogen lamp heater 187 is configured to heat only the central portion in the axial direction of the fixing roller 183 (central light distribution), and the filament 188b of the halogen lamp heater 188 covers the entire axial direction of the fixing roller 183. The filament 189b of the halogen lamp heater 189 is configured to heat only the axial end portion of the fixing roller 183 (end portion light distribution).

As shown in FIG. 3, the pressure roller 184 is urged in a direction approaching the fixing roller 183 by an elastic member (not shown) and pressed against the fixing roller 183, thereby forming a fixing nip with the fixing roller 183. However, it rotates as the fixing roller 183 rotates.
Further, the external heating roller 185 contacts the pressure roller 184 and rotates with the rotation of the pressure roller 184.
The pressure roller 184 may be driven and rotated by a rotation driving unit such as a motor (not shown) under the control of the control unit 10.

  The fixing roller 183 and the pressure roller 184 heat and press the sheet P while sandwiching the sheet P as a recording medium at the fixing nip and transporting the sheet P in the transport direction R indicated by an arrow in FIG. As a result, the fixing roller 183 and the pressure roller 184 melt and fix the toner on the paper P. The temperature of the fixing roller 183 when coming into contact with the paper P is, for example, in a range of 180 ° C. or higher and 200 ° C. or lower. Accordingly, the halogen lamp heaters 187 to 189 heat the fixing roller 183 so that the fixing roller 183 reaches this temperature.

  As shown in FIG. 1, the transport unit 19 includes a plurality of paper transport rollers that transport paper by rotating while sandwiching the paper, and transports the paper through a predetermined transport path. The transport unit 19 includes a reversing mechanism 191 that reverses the front and back of the paper on which the fixing process has been performed by the image fixing unit 18 and transports the paper to the secondary transfer roller 175. In the image forming apparatus 1, when images are formed on both sides of a sheet, the reversing mechanism 191 reverses the front and back of the sheet to form images on both sides, and then the sheet is discharged to the discharge tray 23. When an image is formed only on one side of the paper, the paper on which the image is formed on one side is discharged to the paper discharge tray 23 without reversing the front and back of the paper by the reversing mechanism 191.

  Further, the switching detection unit 20 detects switching of the paper size (width in the direction perpendicular to the conveyance direction) under the control of the control unit 10 and outputs the detected information to the control unit 10. For example, the switching detection unit 20 detects a change in paper size based on the set job information. Further, for example, the switching detection unit 20 detects the switching of the paper size based on the selection state of the paper feed tray.

[2. Description of operation of image forming apparatus]
Here, the operation of the image forming apparatus 1 will be described with reference to the flowchart of FIG.
The control unit 10 controls the detection unit 20 to combine a plurality of jobs and perform continuous fixing processing without setting a standby state between jobs (hereinafter referred to as JOB combination). ), It is determined whether or not the paper size is switched (step S51).

  If the control unit 10 determines that there is no change in the paper size in the job integration (step S51: No), the control unit 10 performs normal temperature control (step S56), and proceeds to step S57.

  On the other hand, when the control unit 10 determines that there is a change in the paper size in the job integration (step S51: Yes), it is determined whether or not the number of sheets passed until the paper size is changed is a predetermined value or more. Judgment is made (step S52).

  For example, the control unit 10 determines whether or not the number of passing sheets until the paper size is switched is 2000 or more. This is because the surface temperature at the end of the fixing roller 183 and the pressure roller 184 is not saturated when the number of sheets passed until the paper size is switched is less than a predetermined value. This is because a large overshoot or undershoot does not occur at the time of replacement.

  If the control unit 10 determines that the number of sheets to be passed until the sheet size is switched is not greater than or equal to a predetermined value (step S52: No), the control unit 10 performs normal temperature control (step S56), and proceeds to step S57. .

  On the other hand, when the control unit 10 determines that the number of sheets to be passed until the paper size is switched is greater than or equal to a predetermined value (step S52: Yes), the heating pattern after the switching of the paper size is determined (step S53). ).

  For example, FIG. 6 is an explanatory diagram illustrating an example of a heating pattern when an A4 size sheet is conveyed in the longitudinal direction after the sheet size is switched (A4S), and FIG. 7 is a diagram after the sheet size is switched. FIG. 6 is an explanatory diagram illustrating an example of a heating pattern when an A4 size sheet is conveyed in a short direction (A4).

  As shown in FIG. 6, when the width of the A4 size sheet in the longitudinal direction is equal to or less than the width L1 of the filament 187b of the central light distribution halogen lamp heater 187, for example, the central light distribution halogen lamp heater 187 is used as the main heater. And a halogen lamp heater 188 having a light distribution in the entire area is used as a sub heater. Then, the main heater is turned on (ON) 100%, and the sub heater is HCD controlled.

  Here, the HCD control is also based on the conventional ON / OFF control in which the halogen lamp heater is turned on (turned on) or turned off (turned off) based on the detected temperature of the fixing roller 183 to control the temperature of the fixing roller 183. This is a control method for performing subdivided temperature control.

  For example, in a predetermined cycle of the AC waveform, by appropriately selecting a half wave of the AC waveform and supplying it to the halogen lamp heater, it is possible to perform temperature control in which the duty ratio in the predetermined cycle is finely controlled.

  Specifically, the control unit 10 applies a trigger signal to the gate of a switching element such as a thyristor or a bidirectional thyristor (triac) in synchronization with the zero-cross signal that detects the zero-cross point of the AC waveform. By controlling ON / OFF of the switching element, a drive signal appropriately selecting a half wave of the AC waveform is generated and supplied to the halogen lamp heater.

  Further, as shown in FIG. 7, the width of the A4 size sheet in the short direction is larger than, for example, the width L1 of the filament 187b of the halogen lamp heater 187 of the center light distribution, and the halogen lamp heater 188 of the entire area light distribution. When the width L2 is smaller than the width L2, the halogen lamp heater 188 with the entire light distribution is used as the main heater, and the halogen lamp heater 187 with the central light distribution is used as the sub heater. Then, the main heater is turned on (ON) 100%, and the sub heater is HCD controlled.

  For the halogen lamp heater 189 having an end light distribution, which is an auxiliary heater, conventional ON / OFF control is performed as necessary.

  Then, the control unit 10 determines the retroactive number of sheets (step S54), and performs temperature control by the heating pattern after switching of the paper size at a timing that is retroactive from the paper before switching of the paper size to be fixed last. Start (step S55).

  For example, when the paper size is switched from the longitudinal direction of the A4 size paper (FIG. 7) to the short direction of the A4 size paper (FIG. 6), the control unit 10 arranges the entire area in the printing temperature saturation state. Even if the temperature at the edge of the sheet drops due to the temperature control of the light sub-heater, the fixing quality can be ensured and the number of retroactive sheets is determined within a range that does not affect the main heater of the central light distribution.

  Further, for example, when the paper size is switched from the short side direction of the A4 size paper (FIG. 6) to the long side direction of the A4 size paper (FIG. 7), the control unit 10 is in a saturated printing temperature state. The number of retroactive sheets is determined within a range that does not affect the temperature rise at the non-sheet-passing edge even if the main heater with light distribution in the entire area is turned on 100% (to ensure the stability of conveyance).

  For example, when the number of sheets to be passed until the paper size is switched is 2000, and the retroactive number is 3, the control unit 10 starts from the 1997th sheet (3 sheets before the paper size switching) and changes the paper size. Start temperature control by heating pattern after switching.

  FIG. 8 is an explanatory diagram illustrating an example of evaluation results of the example and the comparative example. In FIG. 8, the fixing quality, the conveyance stability, and the productivity were evaluated with respect to the presence / absence of JOB coupling and the switching of paper size (from large to small, or from small to large).

  As can be seen from FIG. 8, when the job is not joined as in the condition 3 and the condition 4, in other words, in the case of having the standby state, the productivity is poor, but the fixing quality and the conveyance stability are both in the example and the comparative example. no problem.

  On the other hand, when the paper size is switched from large to small as in the comparative example of Condition 1, the overshoot of the end temperature of the fixing roller 183 is large, and the stability of paper conveyance is ensured. I can't.

  For example, as shown in FIG. 9, in the example in the condition 1, the overshoot of the end temperature characteristic CH91 is about 10 ° C., whereas in the comparative example in the condition 1, as shown in FIG. The overshoot of the part temperature characteristic CH101 is about 15 ° C., and the stability of the sheet conveyance cannot be ensured. Note that CH92 and CH102 in the figure are temperature characteristics at the center.

  Further, when the paper size is switched from small to large as in the comparative example of condition 2, the undershoot of the end temperature of the fixing roller 183 is large, and the fixing quality cannot be ensured. .

  For example, as shown in FIG. 11, the undershoot of the end temperature characteristic CH111 is about 15 ° C. in the example in the condition 2, whereas in the comparative example in the condition 2, as shown in FIG. The undershoot of the partial temperature characteristic CH121 is about 20 ° C., and fixing quality cannot be ensured. Note that CH112 and CH122 in the figure are temperature characteristics at the center.

  Finally, the control unit 10 determines whether or not to end printing (step S57). When it is determined that the printing is not ended (step S57: No), the control unit 10 returns to step S51 and determines that the printing is ended. (Step S57: Yes), printing is terminated.

  As described above, in the image forming apparatus 1 that continuously performs fixing processing of sheets having different widths in the direction perpendicular to the conveyance direction without setting the standby state, the control unit 10 switches the measured temperature and the sheet size. The heating pattern after the paper size change is determined based on the detection result of the paper, and the temperature according to the heating pattern after the paper size change at a timing that is retroactive from the paper before the paper size change to be fixed last. By starting the control, the undershoot and overshoot that occur can be suppressed.

(Modification 1)
In the description of the embodiment, the timing of switching the external heater 190 from ON to OFF when the paper size is switched from large to small is a predetermined time after the paper size is switched. However, it is possible to suppress overshoot after switching the paper size by turning off the external heater 190 in accordance with the timing of switching the paper size.

  For example, as shown in FIG. 13, in the embodiment in Condition 1, the overshoot of the end temperature characteristic CH131 is reduced to about 5 ° C. by turning off the external heater 190 in accordance with the sheet size switching timing. It can be seen that the overshoot (about 10 ° C.) of the end temperature characteristic CH91 shown in FIG. 9 is improved.

  As described above, according to the first modification, the temperature control by the heating pattern after switching the paper size is started at a timing that is retroactive from the paper before the switching of the paper size to be fixed last. The overshoot that occurs can be suppressed by turning off the external heater 190 in accordance with the timing of switching the paper size.

  In the description of the embodiment, an example is given in which the retroactive sheet count is 3 when the number of sheets to be passed until the sheet size is switched is 2000 or more. The retroactive number of sheets is determined based on at least one of the conditions such as the width of the sheet, the basis weight of the sheet, and the number of sheets to be passed, or a combination thereof.

  In the description of the embodiment, as shown in FIGS. 6 and 7, the heating pattern is such that the main heater is turned on (ON) and the sub heater is HCD controlled. The heating pattern may be determined by control or a combination thereof.

  For example, in the case of ON / OFF control, when the temperature is controlled only by the main heater, when the main heater is ON / OFF controlled, and when the temperature is controlled by both the main heater and the sub heater, the main heater is 100% lit (ON), ON / OFF control of sub heater.

  Further, for example, in the case of HCD control, when the temperature is controlled only by the main heater, the main heater is controlled by HCD, and when the temperature is controlled by both the main heater and the sub heater, the main heater and the sub heater are controlled by HCD.

  Further, in the case of these combinations, when temperature control is performed by both the main heater and the sub heater, the main heater is turned on (ON) and the sub heater is HCD controlled. Alternatively, the main heater is HCD controlled and the sub heater is turned on (ON) 100%.

  In the description of the embodiment, the image fixing unit 18 configures a nip unit that sandwiches and conveys the paper P while the fixing roller 183 and the pressure roller 184 include a heating roller that is a heating member, A fixing belt, and the fixing belt is stretched between a heating roller and a fixing roller 183, and the fixing roller 183 and the pressure roller 184 sandwich the paper P through the fixing belt and convey it. You may make it comprise.

  In the description of the embodiment, for example, a unit for image formation is provided for each color such as Y (yellow), M (magenta), C (cyan), K (black), and a color image is formed on the paper P. The image forming apparatus 1 to be formed has been illustrated, but is not limited to this example, and may be an image forming apparatus that forms a monochrome image, for example.

  In the description of the embodiment, paper is exemplified as the recording medium. However, the recording medium is not limited to paper, and may be any sheet that can form and fix a toner image. , Non-woven fabric, plastic film, leather, etc.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Control part 18 Image fixing part 20 Switching detection part (detection part)
183 Fixing roller 184 Pressure roller 185 Outside heating roller 186 Temperature detection unit (measurement unit)
187, 188, 189 Halogen lamp heater (heating unit)
190 External heater (external heating part)
P paper (recording medium)

Claims (8)

A plurality of heating units with different light distributions for heating a fixing roller of an image fixing unit that heats and pressurizes the recording medium on which the toner is transferred to fix the toner to the recording medium;
A measuring unit for measuring the surface temperature of the fixing roller;
A detection unit for detecting switching from the first recording medium to a second recording medium having a width different from that of the first recording medium in a direction perpendicular to the conveyance direction;
A heating pattern for the second recording medium is determined based on the measurement temperature of the measurement unit and the detection result of the detection unit, and the timing is traced back by a predetermined retrospective number from the first recording medium to be fixed last. A control unit for starting control of the heating unit by a heating pattern;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the control unit determines the heating pattern based on a width in a direction perpendicular to a conveyance direction of the second recording medium.   3. The image formation according to claim 1, wherein the plurality of heating units have a light distribution pattern that is parallel to a conveyance direction of the second recording medium and symmetrical with respect to a straight line passing through the center. apparatus.   Based on the detection result of the detection unit, the control unit sets one of the plurality of heating units having different light distributions as a main heating unit that mainly heats, and sets the other as a sub-heating unit that supplementarily heats the other. The image forming apparatus according to claim 1, wherein a heating pattern is determined.   The image forming apparatus according to claim 1, wherein the controller determines the heating pattern by ON / OFF control, HCD control, or a combination thereof.   6. The image according to claim 1, wherein the detection unit detects switching of the second recording medium based on set job information or a selection state of a paper feed tray. 6. Forming equipment.   7. The control unit according to claim 1, wherein the control unit determines the retroactive sheet number based on at least one of a width of the recording medium, a basis weight of the recording medium, a sheet passing number, or a combination thereof. The image forming apparatus according to one item. An external heating unit for heating the pressure roller of the image fixing unit;
2. The control unit according to claim 1, wherein when the width of the second recording medium is smaller than the width of the first recording medium, the control unit turns off the external heating unit at a timing when the recording medium is switched. 8. The image forming apparatus according to any one of items 1 to 7.

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