JP2019144451A - Image formation apparatus - Google Patents

Abstract

To provide an image formation apparatus which can shorten the preheating time when the image width of a toner image of a succeeding recording material is wider than an immediately preceding recording material.SOLUTION: In a case of continuously forming toner images on a plurality of recording materials, control means 23 shortens the control period of the lighting ratios of the first and second heating elements 4b1, 4b2 when the image width of the toner image detected by image width detection means 21 is wider than the immediately preceding recording material in which the toner image is formed immediately precedingly, and switches the lighting ratio setting of the first and second heating elements in accordance with the power detection result by power detection means 25 when the toner image is fixed on the immediately preceding recording material.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer.

  The electrophotographic printer includes an image forming unit that forms a toner image on a recording material, and a fixing unit (fixing device) that fixes the toner image formed on the recording material to the recording material. In the image forming unit, the toner image carried on the photosensitive drum (image carrier) is transferred to a recording material by a transfer member. The fixing unit includes a cylindrical film, a plate-shaped heater that contacts the inner surface of the film, and a roller that forms a nip portion together with the heater via the film, and carries an unfixed toner image at the nip portion. The toner image is fixed on the recording material by heating the recording material to be sandwiched and conveyed.

  In the above printer, when a small size recording material is continuously printed at the same print interval as that of the large size recording material, the non-passage area of the heater through which the small size recording material does not pass may be excessively heated (temperature increase of the non-passing portion). Are known. Therefore, it is required to suppress the temperature rise of the non-passing portion of the heater from the viewpoint of power saving of the printer.

  Patent Document 1 discloses a fixing device that controls the amount of heat generated by each of a plurality of resistance heating elements of a heater for each size of a recording material. In Patent Document 1, the heater has a first heating element on the substrate, the first heating element whose heat generation amount gradually decreases from the center in the direction orthogonal to the recording material conveyance direction, and the direction orthogonal to the recording material conveyance direction. And a second heating element whose calorific value gradually increases from the center toward the end. And the lighting ratio of each heat generating body is controlled. By this lighting ratio control, the heat generation amount can be continuously changed in the direction orthogonal to the recording material conveyance direction according to the recording material size, so that the temperature rise of the non-passing portion of the heater can be effectively suppressed. .

JP 2010-164930 A

  When a toner image is continuously formed on a plurality of recording materials by a printer equipped with the fixing device disclosed in Patent Document 1, the image width of the toner image of the subsequent recording material is set in the direction orthogonal to the recording material conveyance direction. It may be wider than the preceding (immediately preceding) recording material. In this case, for the preceding recording material, when the non-passing area of the heater is controlled to a low temperature and the passing area is controlled to a high temperature, the image of the area that was the non-passing area of the preceding recording material for the subsequent recording material In order to newly acquire information, a preheating time for raising the temperature of the area is required. Therefore, it is necessary to control to increase the lighting ratio of the second heating element in the area where the image information is newly acquired.

  However, in the printer described above, productivity decreases when the preheating time becomes long, and therefore it is required to shorten the preheating time.

  An object of the present invention is to form an image capable of shortening the preheating time for raising the temperature of the image width end portion of the subsequent toner image when the image width of the toner image of the subsequent recording material is wider than that of the immediately preceding recording material. To provide an apparatus.

In order to achieve the above object, an image forming apparatus according to the present invention includes:
An image forming apparatus for forming an image on a recording material,
An image carrier;
A transfer member for transferring a toner image carried by the image carrier to a recording material;
A first heating element that reduces the amount of heat generation from the center in the direction orthogonal to the recording material conveyance direction toward the end, and a first heat generation amount that increases from the center in the direction orthogonal to the recording material conveyance direction toward the edge. A heating member having a second heating element and a substrate provided with the first and second heating elements;
A cylindrical fixing member that rotates while contacting the substrate and the inner peripheral surface, heats the recording material carrying the toner image, and fixes the toner image on the recording material by heating;
In an image forming apparatus having
Lighting ratio control means for controlling the lighting ratio of the first heating element and the second heating element at a constant period;
Image width detection means for detecting an image width in a direction orthogonal to the recording material conveyance direction of the toner image transferred from the image carrier to the recording material;
Power detection means for detecting power supplied to the first heating element and the second heating element;
Control means for setting a lighting period control period of the first heating element and the second heating element, and a lighting ratio setting of the second heating element;
Have
When continuously forming toner images on a plurality of recording materials, the control means has a wider image width of the toner image detected by the image width detection means than the recording material immediately before the toner image was formed. In this case, the control period of the lighting ratio is shortened, and the lighting ratio setting is switched according to the power detection result by the power detection means when the toner image is fixed on the immediately preceding recording material.

  According to the present invention, when the image width of the toner image of the succeeding recording material is wider than that of the immediately preceding recording material, image formation capable of shortening the preheating time for raising the temperature of the image width end of the succeeding toner image Provision of the device can be realized.

Sectional drawing which shows schematic structure of the image forming apparatus which concerns on Example 1. FIG. Sectional view showing schematic configuration of fixing device Figure when the fixing device is viewed from the upstream side in the recording material conveyance direction X Sectional drawing which shows schematic structure of heater, and front view Diagram showing the heat distribution of the heater Block diagram showing the configuration of the heater lighting ratio control system The figure which shows the relationship between the lighting ratio of the main heating element of a heater and a sub-heating element, and the higher temperature profile of a sub thermistor Main heating element, sub heating element lighting ratio table The figure for demonstrating the image width detection process of an image width detection part The figure which shows the relationship between upper limit threshold temperature according to image width and lower limit threshold temperature Lighting ratio control flowchart Sub-flow chart of preheating mode shown in FIG. 11A The figure which shows the temperature profile of the lighting ratio setting in the flowchart of lighting ratio control, a setting change threshold time, and a sub thermistor. The figure which shows the lighting profile setting in the flowchart of the lighting ratio control of Experimental example 1, setting change threshold time, and the temperature profile of a sub thermistor. The figure which shows the lighting profile setting in the flowchart of the lighting ratio control of the comparative example 1, setting change threshold time, and the temperature profile of a sub thermistor. The figure which shows the temperature profile of the lighting ratio setting in the flowchart of the lighting ratio control of the comparative example 2, setting change threshold time, and a sub thermistor. Switching table for lighting ratio setting according to power value FIG. 10 is a diagram for explaining image width detection processing of an image width detection unit of the image forming apparatus according to the second embodiment. Example 2 and Example 3 lighting ratio control flowchart Example 2 and Example 3 lighting ratio control flowchart The figure which shows the relationship between upper limit threshold temperature according to image width and lower limit threshold temperature The figure which shows the temperature profile of the lighting ratio setting in the flowchart of the lighting ratio control of Example 2, setting change threshold time, and the sub thermistor 14. FIG. FIG. 10 is a diagram for explaining image width detection processing of an image width detection unit of an image forming apparatus according to Embodiment 3; The figure which shows the temperature profile of the lighting ratio setting in the flowchart of the lighting ratio control of Example 3, setting change threshold time, and the sub thermistor 14. FIG. The figure which shows the temperature threshold value of the lighting ratio change which shows the measurement time of the time required for the preheating of Examples 1, 2, and 3, Experimental Example 1, and Comparative Examples 1 and 2 and power consumption

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Although the preferred embodiment of the present invention is an example of the best embodiment of the present invention, the present invention is not limited to the following embodiment, and various other configurations are within the scope of the idea of the present invention. It is possible to replace with.

[Example 1]
<Image forming apparatus 100>
With reference to FIG. 1, an image forming apparatus 100 according to the present exemplary embodiment will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of an example of an image forming apparatus (full color printer in this embodiment) 100 using an electrophotographic recording technique.

  The image forming apparatus 100 includes an image forming unit A and a fixing device B as a fixing unit.

  The image forming unit A that forms an image on the recording material P using toner has four image forming stations SY, SM, SC, and SK of yellow, magenta, cyan, and black. Each image forming station includes a photosensitive drum 101 (first image carrier), a charging member 102, a laser scanner 103, a developing device 104, a cleaner 105 for cleaning the outer peripheral surface of the photosensitive drum, and a transfer member 106. ,have.

  The image forming unit A further transfers an endless belt 107 (second image carrier) that carries the toner image transferred from each photosensitive drum 101 by the transfer member 106, and transfers the toner image from the belt to the recording material P. And a secondary transfer member 108.

  In the image forming apparatus 100, the outer peripheral surface (surface) of the photosensitive drum 101 that rotates at a predetermined process speed in the arrow direction is uniformly charged to a predetermined polarity and potential by the charging member 102. The scanner 103 emits a laser beam L to scan and expose the charging surface of the photosensitive drum 101. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 101. The electrostatic latent image on the surface of the photosensitive drum 101 is developed as a toner image with toner by the developing device 104.

  The recording material P stored in the cassette 109 in the apparatus main body 100A is fed out one by one as the roller 110 rotates. The recording material P is supplied to the roller 112 by the rotation of the roller 111. The recording material P is conveyed to the secondary transfer portion formed by the belt 107 and the secondary transfer member 108 by the rotation of the roller 112, and the toner image on the surface of the photosensitive drum is transferred onto the recording material in the secondary transfer portion. The The recording material P carrying an unfixed toner image is sent to the fixing device B, and the toner image is fixed on the recording material by the fixing device. The recording material P exiting the fixing device B is discharged to the tray 114 by the rotation of the roller 113.

<Fixing device B>
The fixing device B will be described with reference to FIGS. The fixing device B shown in FIGS. 2 and 3 is a film heating type device. FIG. 2 is a cross-sectional view illustrating a schematic configuration of the fixing device B. FIG. 3 is a view of the fixing device B when viewed from the upstream side in the recording material conveyance direction X.

  The fixing device B includes a cylindrical film 1 as a fixing member, a holder 2 as a support member, a stay 3 as a reinforcing member, a ceramic heater 4 as a heating member, and a roller 5 as a pressure member, And a flange 6 as a regulating member.

<Roller 5>
The roller 5 includes a metal core 5a, an elastic layer 5b provided on the outer peripheral surface of the metal core, and a release layer 5c provided on the outer peripheral surface of the elastic layer. The elastic layer 5b is made of heat-resistant silicone rubber or fluorine rubber, and has a thickness of 3.5 mm. The material of the release layer 5c is a fluororesin, and the thickness is 30-50 μm. The diameter of the roller 5 is 25 mm. In a direction Y orthogonal to the recording material conveyance direction X, both ends of the cored bar 5a are rotatably supported by the side plate 10 of the fixing device B via bearings 11.

<Holder 2>
The holder 2 made of heat-resistant resin inserted through the hollow portion of the film 1 supports the heater 4 along a direction Y orthogonal to the recording material conveyance direction X by a recess 2a provided on a flat surface on the roller 5 side. . The holder 2 also serves as a guide member that guides the rotation of the film 1. The material of the holder 2 is PPS.

<Heater 4>
The heater 4 will be described with reference to FIGS. 4A is a cross-sectional view showing a schematic configuration of the heater 4, and FIG. 4B is a front view showing a schematic configuration of the heater 4 when viewed from the holder 2 side. In (b), illustration of the protective layer 4c is omitted.

  The heater 4 has an elongated ceramic substrate (aluminum nitride substrate in this embodiment) 4a. On the flat surface on the holder 2 side of the substrate 4a, a first resistance heating element 4b1 that generates heat by energization is provided in the longitudinal direction of the substrate at each of an upstream end and a downstream end in the recording material conveyance direction X of the substrate. It is provided along.

  On the flat surface on the holder 2 side of the substrate 4a, a second resistance heating element 4b2 that generates heat when energized is further provided in the center of the recording material conveyance direction X of the substrate 4a along the longitudinal direction of the substrate.

  Each of the heating elements 4b1 and 4b2 is set and formed on the substrate 4a with a conductive paste containing a silver palladium (Ag / Pd) alloy. Regarding each of the heating elements 4b1 and 4b2, the thickness is 10 μm, and the width in the recording material conveyance direction X is 1 mm.

  A protective layer (a glass coat having a thickness of 30 μm in this embodiment) 4c is further provided on the flat surface of the substrate 4a on the holder 2 side to ensure protection and insulation of the heating elements 4b1 and 4b2. The flat surface on the holder 2 side further includes an electrode 4d1 electrically connected to one end of the heating element 4b2, an electrode 4d2 electrically connected to one end of the heating element 4b1, and other heating elements 4b1 and 4b2. And a common electrode 4d3 electrically connected to the end.

  On the other hand, on the flat surface opposite to the holder 2 side of the substrate 4a, a sliding layer 4e for relaxing the frictional force with the inner peripheral surface (inner surface) of the film 1 is provided. The material of the sliding layer 4e is polyimide.

  Setting of the heating elements 4b1 and 4b2 will be described with reference to FIG. FIG. 5 shows the heat generation distribution in the direction Y orthogonal to the recording material conveyance direction X of the heating elements 4b1 and 4b2.

  As shown in FIG. 4B, the setting of the heating element 4b1 is continuously thicker from the center to the end in the direction Y perpendicular to the recording material conveyance direction X of the heating element. Therefore, the heat generation amount of the heating element 4b1 gradually decreases from the center in the direction Y orthogonal to the recording material conveyance direction X toward the end as shown in FIG. Hereinafter, the heating element 4b1 is referred to as a main heating element.

  On the other hand, the setting of the heating element 4b2 is continuously narrowed from the center to the end in the direction Y perpendicular to the recording material conveyance direction X of the heating element. Therefore, the heat generation amount of the heating element 4b2 gradually increases from the center of the direction Y orthogonal to the recording material conveyance direction X toward the end as shown in FIG. Hereinafter, the heating element 4b2 is referred to as a sub-heating element.

  By controlling the lighting ratio of the main heating element 4b1 and the sub-heating element 4b2 in accordance with the recording material P size, the large size recording material passes in the direction Y orthogonal to the recording material conveyance direction X, and the small size recording material. The temperature increase of the non-passing part in the non-passing region where the gas does not pass can be effectively suppressed.

  Here, the main thermistor 13 and the sub-thermistor 14 as temperature detecting members will be described with reference to FIG.

  In the direction Y orthogonal to the recording material conveyance direction X, the main thermistor 13 is in contact with the center of the sub-heating element 4b2. Therefore, the main thermistor 13 detects the temperature of the passage region through which both the small size recording material and the large size recording material of the heater 4 pass. The sub thermistor 14 is in contact with both ends of the sub heat generating element 4b2. Therefore, the sub-thermistor 14 detects the temperature of the non-passing area where the large size recording material of the heater 4 passes and the small size recording material does not pass. These thermistors 13 and 14 are supported by the holder 2 (see FIG. 2).

<Film 1>
As shown in FIG. 2, the film 1 includes a base layer 1a, an elastic layer 1b provided on the outer peripheral surface of the base layer, and a release layer 1c provided on the outer peripheral surface of the elastic layer. The material of the base layer 1a is metal (SUS in this embodiment), and the thickness is 30 μm. The material of the elastic layer 1b is silicone rubber or fluororubber, and the thickness is 200 to 800 μm. The material of the release layer 1c is a fluororesin, and the thickness is 15 to 25 μm. The diameter of the film 1 is 24 mm.

<Flange 6>
As shown in FIG. 3, the flange 6 made of heat resistant resin is supported by the frame 10 of the fixing device B in the direction Y orthogonal to the recording material conveyance direction X. When the film 1 moves in the direction Y orthogonal to the recording material conveyance direction X, or in the direction opposite to the direction, the flange 6 has its end face 1e abutting against the restriction surface 6a on the film side of the flange. To regulate the movement of the film. Each flange 6 supports both ends of the holder 2 and the stay 3.

<Stay 3>
As shown in FIG. 2, in the direction Y orthogonal to the recording material conveyance direction X, the metal stay 3 inserted through the hollow portion of the film 1 is installed on the flat surface opposite to the roller 5 side of the holder 2. Has been. This stay 3 serves to reinforce the holder 2.

  As shown in FIG. 3, both ends of the stay 3 are pressurized in the recording material thickness direction Z by the pressure spring 12. In this embodiment, the pressurizing spring 12 applies a pressing force of about 100 N to 250 N (about 10 kgf to about 25 kgf) to the stay 3. The stay 3 presses the holder 2 against the inner peripheral surface (inner surface) of the film 1 by the pressing force of the pressure spring 12 to press the outer peripheral surface (front surface) of the film against the outer peripheral surface (front surface) of the roller 5. As a result, the elastic layer 5b of the roller 5 is crushed and elastically deformed to form a nip portion N having a predetermined width in the recording material conveyance direction X between the roller surface and the film surface.

<Heat fixing processing operation>
The heat fixing processing operation of the fixing device B will be described with reference to FIGS. 2, 3, and 4. FIG.

  The driving force of the motor M (see FIG. 3) is transmitted to the metal core 5a of the roller 5 through the gear G, whereby the roller rotates in the direction of the arrow shown in FIG. The film 1 rotates in the direction of the arrow shown in FIG. 2 following the rotation of the roller 5 while the inner surface of the film is in contact with the sliding layer 4 e of the substrate 4 a of the heater 4.

  Electric power is supplied to the electrodes 4d1, 4d2, and 4d3 of the heater 4 via a power supply connector (not shown), whereby the main heating element 4b1 and the sub-heating element 4b2 generate heat, and the heater rapidly rises in temperature.

  A control unit 23 (see FIG. 6) as a control means takes in the detected temperature output from the thermistors 13 and 14 and supplies the detected temperature to the main heating element 4b1 and the sub-heating element 4b2 so as to maintain the detected temperature at a predetermined target value. Control the amount of power supply. As a result, the film 1 is maintained at a predetermined fixing temperature.

  The recording material P carrying the unfixed toner image t is heated while being nipped and conveyed by the nip portion N, whereby the toner image is fixed on the recording material.

<Explanation of heater lighting ratio control>
The heater lighting ratio control will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the heater lighting ratio control system according to the image width detection result.

  The image forming apparatus 100 includes a video controller 20, an image width detection unit (image width detection unit) 21, a lighting ratio control unit (lighting ratio control unit) 22, a control unit (control unit) 23, a drive circuit unit 24, and power detection. Part (power detection means). The video controller 20 receives a print signal from an external information device and controls the image forming unit A and the fixing device B. The image width detection unit 21 detects an image width in a direction Y orthogonal to the recording material conveyance direction X of the toner image transferred from the photosensitive drum 101 to the recording material P. The lighting ratio control unit 22 controls the lighting ratio of the main heating element 4b1 and the sub heating element 4b2 at a constant period.

  The control unit 23 includes a CPU and a memory such as a RAM and a ROM. In the memory, a program for executing predetermined lighting ratio control, a lighting period control cycle of the main heating element 4b1 and the sub heating element 4b2, and a lighting ratio setting of the main heating element and the sub heating element are set. Has been. The drive circuit unit 24 drives the main heating element 4b1 and the sub heating element 4b2. The power detection unit 25 detects the power supplied to the main heating element and the sub heating element.

<Description of Lighting Ratio Control of Main Heating Element 4b1 and Sub Heating Element 4b2>
The lighting ratio control when 80 g of A4 size paper Oce redlabel is continuously passed through the nip portion N at a process speed of 222 mm / sec and 45 ppm from room temperature will be described with reference to FIGS.

  FIG. 7 shows the relationship between the lighting ratio of the main heating element 4b1 and the sub-heating element 4b2 of the heater 4 and the higher temperature profile of the sub-thermistor 14. That is, FIG. 7 shows the result of measuring the difference between the detected temperature of the higher thermistor 14 and the main thermistor for each number of sheets while controlling the detected temperature of the main thermistor 13 at the target value 180 ° C. (reference temperature). . However, FIG. 7 shows the measurement results that do not depend on the image width detection results described later.

  FIG. 8 is a lighting ratio table illustrating, as a table, ratios in which the lighting ratio of either the main heating element 4b1 or the sub-heating element 4b2 is changed stepwise.

  In the lighting ratio table of FIG. 8, it is possible to select from the first stage to the 20th stage so that the ratio of the heat generation amount in the non-passage area to the heat generation amount in the passage area gradually decreases. In the sixth stage, the lighting ratios of the main heating element 4b1 and the sub heating element 4b2 are both 100%.

  From the first stage to the sixth stage, by increasing the lighting ratio of the main heating element 4b1, the ratio of the heat generation amount in the non-passing region to the heat generation amount in the passing region is gradually reduced. In the sixth to twentieth stages, the ratio of the amount of heat generated in the non-passing area to the amount of heat generated in the passing area is gradually decreased by decreasing the lighting ratio of the sub-heating element 4b2.

  In FIG. 7, the detected temperature of the sub-thermistor 14 in the non-passing area of A4 size paper (hereinafter referred to as paper) gradually increases as the paper passes through the nip N continuously. For this reason, when the detected temperature of the sub-thermistor 14 exceeds the temperature that is higher than the reference temperature by the upper threshold temperature, the control unit 23 changes the lighting ratio setting according to the lighting ratio table of FIG.

  Specifically, the upper limit threshold temperature is 18 ° C., the setting change threshold time is 1.2 seconds, and when a temperature higher than the reference temperature by 18 ° C. or more is detected by the sub-thermistor 14 for 1.2 seconds or more, The control unit 23 changes the lighting ratio setting. That is, control is performed such that the amount of heat generated at both ends of the sub-heating element 4b2 is reduced and the detection temperature of the sub-thermistor 14 is lowered.

  The setting change threshold time set to 1.2 seconds above is optimized from the viewpoint of the responsiveness of the detected temperature of the sub-thermistor 14.

  That is, when the lighting ratio is shorter than 1.2 seconds, after the lighting ratio of the main heating element 4b1 and the sub heating element 4b2 is changed, the main heating element 4b1 and the sub heating element are detected before the sub-thermistor 14 detects a temperature change due to this lighting ratio. The lighting ratio of 4b2 is changed continuously. For this reason, if the temperature rises too much, the amount of heat generated at both ends of the sub-heating element 4b2 is controlled to be excessively reduced until the temperature of the non-passing region is lowered. As a result, the temperature detected by the sub-thermistor 14 may drop sharply, and the fixability at the edge of the toner image may deteriorate in the direction Y perpendicular to the recording material transport direction X.

  On the other hand, if it is longer than 1.2 seconds, the temperature increase in the non-passing region that occurs until the setting change threshold time elapses is allowed. As a result, the temperature detected by the sub-thermistor 14 is significantly higher than that of the main thermistor 13, and as a result, a hot offset may occur at the end of the toner image. Therefore, 1.2 seconds was set in consideration of the balance between the two.

  When the temperature is too low, that is, when the detected temperature of the sub-thermistor 14 is lower than the reference temperature by the lower threshold temperature than the setting change threshold time, the controller 23 changes the lighting ratio setting according to the lighting ratio table of FIG. Let Specifically, the lower threshold temperature is 5 ° C., and when the sub-thermistor 14 detects a temperature 5 ° C. or more higher than the reference temperature for 1.2 seconds or more, the control unit 23 changes the lighting ratio setting. . That is, control is performed so as to increase the amount of heat generated at both ends of the sub-heating element 4b2 and raise the detection temperature of the sub-thermistor 14.

<Description of Image Width Detection Unit (Image Width Detection Unit) 21>
The image width detection unit 21 will be described with reference to FIGS. 9 and 10.

  FIG. 9 is a diagram for explaining the image width detection processing of the image width detection unit 21. FIG. 10 is a diagram illustrating the relationship between the upper threshold temperature and the lower threshold temperature corresponding to the image width.

  When the control unit 23 receives a print job (print command) and starts printing the first sheet when continuously forming images on a plurality of sheets, the control unit 23 performs the next from the image width detection unit 21 via the video controller 20. The image width of the toner image formed on the other paper is received.

In the image width detection unit 21, when the toner amount information received by the video controller 20 is an A4 size width 210 mm shown in FIG. 9 and an image width (image area) 180 mm symmetrical with respect to the center of the A4 size width, Let E be the margin (non-image area). The maximum toner loading amount in E <0.1 mg / cm ² (1)
When the condition is satisfied, it is determined that the image width D = 180 mm is detected.

  That is, the image width detection unit 21 detects the image width in the direction Y orthogonal to the recording material conveyance direction X based on whether or not there is a predetermined amount of applied toner outside the image width.

  The control unit 23 sets the above-described upper limit threshold temperature = 18 ° C. and lower limit threshold temperature = 5 ° C. when the expression (1) is satisfied.

  In addition, when the expression (1) is not satisfied, the control unit 23 determines that the image width detection unit 21 has detected an image width> 180 mm, and the upper limit threshold temperature = −8 ° C. and the lower limit threshold temperature = −, as shown in FIG. Set to 24 ° C. Accordingly, the ratio of the heat generation amount of the non-passing region to the heat generation amount of the passage region is easily set so that the temperature of the non-passing region can be increased.

<Description of lighting ratio control according to image width detection result>
The lighting ratio control according to the image width detection result will be described with reference to FIGS. 11A and 11B. FIG. 11A is a flowchart of lighting ratio control. FIG. 11B is a sub-flowchart of the preheating mode S4 of FIG. 11A.

  In S1, a print job is received and continuous printing of a plurality of recording materials is started.

  In S2, it is determined whether or not the nth image width = 180 mm. If the image width is not 180 mm (No), the upper and lower threshold temperatures corresponding to the nth image width are determined in S5, and the setting change threshold time is set to 1.2 seconds in S7. If the image width is 180 mm (Yes), the process proceeds to S3.

  In S3, it is determined whether or not the image width of the (n + 1) th sheet> 180 mm. If the image width> 180 is not satisfied (No), in S6, a condition corresponding to the (n + 1) th image width of 180 mm is determined, specifically, an upper threshold temperature and a lower threshold temperature, and the process proceeds to S7. If the image width is greater than 180 (Yes), the n + 1th sheet is parallel to the nth print in order to ensure the fixability at the edge of the (n + 1) th image width during the nth print. The process proceeds to a preheating mode S4 for preheating the region E at the end.

  In FIG. 11B, in S4a, preheating of the paper edge is started. Simultaneously with the processing of S4a, in S4b, the lighting ratio is set based on the table of FIG. 16 described later according to the power detection result by the power detection unit 25 when fixing the nth toner image t being printed. Switch. Further, in S4c, an upper threshold temperature and a lower threshold temperature corresponding to the (n + 1) th image width are determined, and in S4d, the setting change threshold time is shortened from 1.2 seconds to 0.3 seconds. That is, in S4d, the control period of the lighting ratio is made shorter than a certain period.

  In S4e, as soon as the detected temperature of the sub-thermistor 14 converges to the edge target temperature range corresponding to the (n + 1) th image width, in S104f, the preheating of the sheet edge is finished. Here, the convergence condition of the end target temperature range is that the detected temperature of the sub-thermistor 14 continues for 0.3 seconds or more in the threshold temperature range between the upper limit threshold temperature and the lower limit threshold temperature corresponding to the (n + 1) th image width. Judgment by whether or not.

  As described above, when the preheating mode S4 for preheating the region E at the end of the sheet is finished, the process proceeds to S7.

  In S7, the setting change threshold time is returned to 1.2 seconds again.

  In S8, it is determined whether or not the paper of the print job is final. If it is not final (No), the process proceeds to S9, and if it is final (Yes), the process proceeds to S10.

  In S9, the number of sheets is updated and the process returns to S2.

  Printing is terminated in S10.

  Hereinafter, the flowchart of the lighting ratio control shown in FIGS. 11A and 11B will be described in detail in the case where toner images are continuously formed on a plurality of sheets.

  In response to the print job, continuous printing of n sheets is started (S1).

  In this embodiment, n = 105. Similarly, in Experimental Example 1, Comparative Example 1, and Comparative Example 2 described later, n = 105 sheets. In this embodiment, the fixing device B continuously prints a color image having an image width of 180 mm satisfying the expression (1) from the room temperature state to n = 1 sheet to n = 100 sheets, and then does not satisfy the expression (1). Print a color image. That is, the control unit 23 determines that the toner amount information “image width> 180 mm” is detected by the image width detection unit 21 at the n = 101th sheet during the printing of n = 100th sheet.

  Hereinafter, processes from n = 1 are sequentially described.

  From n = 1 to n = 99, (S2) → (S3) → (S6) → (S7) → (S8) → (S9) is repeated. In (S6), since the (n + 1) th image width = 180 mm, the upper threshold temperature = 18 ° C. and the lower threshold temperature = 5 ° C. are selected according to FIG. In (S7), the lighting ratio is controlled with a setting change threshold time of 1.2 seconds.

  Next, the case of n = 100th sheet will be described.

  Since the image width = 180 mm for the n = 100th image and the image width> 180 mm for the n = 101th image, the process proceeds in the order of (S2) → (S3) → (S4) → (S7).

  In the preheating mode of (S4), at the start of preheating of (S4a), the lighting ratio setting is switched according to the power value (power detection result) for fixing the n = 100th toner image of (S4b). . FIG. 16 shows a switching table for setting the lighting ratio according to the power value. Since the power value detected by the power detection unit 25 when fixing the n = 100th toner image is 621 W, the lighting ratio is set to -3 steps based on the table of FIG. 16, that is, the heat generation in the non-passing area. Switch 3 steps to increase the amount. Further, in (S4c), the conditions corresponding to the image width> 180 mm, specifically, the upper threshold temperature is −8 ° C., that is, 8 ° C. lower than the reference temperature, and the lower threshold temperature is −24 ° C., that is, the reference temperature. The temperature is updated to 24 ° C. higher than

  After that, in (S4d), the setting change threshold time is shortened to 0.3 seconds, and in (S4e), as soon as it converges to the edge target temperature range corresponding to the next image width, in (S4f), the edge preheating of the sheet is finished. To do. Here, the convergence condition of the end target temperature range in (S4e) is as described above.

  When the preheating mode of (S4) ends, the setting change threshold time is returned to 1.2 seconds in (S7). Thereafter, the number of sheets is updated through (S8) and (S9).

  Next, the case of n = 101st sheet to n = 105th sheet will be described.

  Since n = 101th image width> 180 mm, (S2) → (S5) → (S7) → (S8) → (S9) are repeated until the final page n = 105th sheet. Since the image width> 180 mm, in (S5), the upper threshold temperature is set to 18 ° C. and the lower threshold temperature is set to 5 ° C. according to FIG. In (S7), the lighting ratio is controlled based on the detection result of the sub-thermistor 14 every setting change threshold time 1.2 seconds.

  FIG. 12 shows the lighting ratio setting, the setting change threshold time, and the temperature profile of the sub-thermistor 14 in the above-described lighting ratio control flowchart.

  After 100 color images are continuously printed from the room temperature state and the lighting ratio setting of the sub-heating element 4b2 is saturated to 30, n = 100 sheets (preceding (immediately preceding) recording material) are being printed. + 1 = 101 mm sheet (following recording material), and detected an image width> 180 mm. Immediately after that, the edge preheating of the 101st sheet is started so that the detected temperature of the sub-thermistor 4b2 converges to the edge target temperature range corresponding to the image width of the 101st sheet.

  As described above, the power value detected by the power detection unit 25 when fixing the toner image on the 100th sheet is 621 W. Therefore, according to the table of FIG. 16, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is switched to -3 levels, that is, 3 levels so as to increase the amount of heat generated in the non-passing region. In this way, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is immediately switched from 30% at the 20th stage a to 45% at the 17th stage b.

  Next, the upper threshold temperature is updated to 18 ° C., the lower threshold temperature is updated to 5 ° C., and the setting change threshold time (lighting ratio cycle) is shortened to 0.3 seconds, so that the lighting ratio setting is changed from a → b → c. → d → e switch quickly. Thereby, the temperature detected by the sub-thermistor 14 can be converged to the end target temperature range. As a result, the time from the start of preheating to the end of preheating (n + 1 = time required for preheating to raise the temperature of the image width end of the 101st toner image) is 1.5 seconds, impairing productivity. And printing can be continued.

(Experimental example 1)
Experimental example 1 is a case where, after detecting 100 images with an image width of 180 mm, the image width> 180 mm is detected after the 101st image as in the first embodiment. The difference from the first embodiment is that the image is not a color image but a monochrome text image when 100 sheets are continuously printed from the room temperature state. The flowchart of the lighting ratio control according to the image width detection result is the same as that of the first embodiment.

  FIG. 13 shows the lighting ratio setting, the setting change threshold time, and the temperature profile of the sub thermistor 14 in the lighting ratio control flowchart of Experimental Example 1.

  After 100 monochrome text images are printed from room temperature and the lighting ratio setting of the sub-heating element 4b2 converges to 50%, the n = 101th sheet is printed while the n = 100th sheet is printed. Was detected to have an image width> 180 mm. Immediately thereafter, the edge preheating of the 101st sheet is started.

  Since the power value detected by the power detection unit 25 when fixing the toner image on the 100th sheet is 514 W, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is set to -10 steps according to FIG. Then, 10 steps are switched so as to increase the amount of heat generated in the non-passing area. Thus, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is immediately switched from 50% at the 15th stage k to 100% at the 6th stage l.

  Next, the upper limit threshold temperature is updated to 18 ° C., the lower limit threshold temperature is updated to 5 ° C., and the setting change threshold time is shortened to 0.3 seconds, so that the lighting ratio setting is quickly changed from k → l → m → n → o. Switch to As a result, the detected temperature of the sub-thermistor 14 can be converged toward the end target temperature range. As a result, the time from the start of preheating to the end of preheating is 1.6 seconds, and printing can be continued without impairing productivity.

(Comparative Example 1)
In Comparative Example 1, as in Experimental Example 1, after detecting 100 images with an image width of 180 mm, the image width> 180 mm is detected after the 101st image. In Comparative Example 1, the image when 100 sheets are continuously printed from the room temperature state is a monochrome text image, and the process of setting the setting change threshold time of (4d) in the flowchart of FIG. 11B to 0.3 seconds is not performed. 1.2 seconds.

  FIG. 14 shows the lighting ratio setting, the setting change threshold time, and the temperature profile of the sub-thermistor 14 in the flowchart of the lighting ratio control of the first comparative example.

  During the printing of the 100th sheet, the lighting ratio setting of the sub-heating element 4b2 converged to 50%, and the power value detected by the power detection unit 25 was 523W. As a result, according to FIG. 16, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is switched to -10 levels, that is, 10 levels so as to increase the heat generation amount in the non-passing area.

  In this way, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is immediately switched from 50% at the 16th stage f to 100% at the 6th stage g. Thereafter, the lighting ratio setting of the sub-heating element 4b2 is gradually updated from 100% at the 6th stage g to 95% at the 7th stage h with a setting change threshold time of 1.2 seconds. The time from the start of preheating to the end of preheating required 3.6 seconds.

(Comparative Example 2)
In Comparative Example 2, as in Comparative Example 1, after 100 images having an image width of 180 mm are detected, an image width> 180 mm is detected from the 101st image onward. In Comparative Example 2, the image when 100 sheets are continuously printed from the room temperature state is a monochrome text image, and the process of setting the setting change threshold time of (4d) in the flowchart of FIG. 11B to 0.3 seconds is not performed. 1.2 seconds. Moreover, in the comparative example 2, the process which switches to the lighting ratio setting of the sub heat generating body 4b2 of (4b) in the flowchart of FIG. 11B is not performed.

  FIG. 15 shows the lighting ratio setting, the setting change threshold time, and the temperature profile of the sub-thermistor 14 in the lighting ratio control flowchart of the comparative example 2.

  During the printing of the 100th sheet, the lighting ratio setting of the sub-heating element 4b2 converged to 50%, and the power value detected by the power detection unit 25 was 504W. Since the process of (4b) is not performed, immediately after the start of preheating, the lighting ratio setting of the sub-heating element 4b2 is sequentially turned on from 50% at the 16th stage f to 90% at the 8th stage n after the setting change threshold time of 0.3 seconds. Although the ratio setting was changed, the time from the start of preheating to the end of preheating was 2.9 seconds.

  As described above, the image forming apparatus 100 according to the present exemplary embodiment increases the image width end portion of the subsequent toner image when the image width of the toner image of the subsequent recording material is wider than that of the preceding (immediately preceding) recording material. Preheating time for heating can be shortened.

[Example 2]
Another example of the image forming apparatus 100 will be described. FIG. 16, FIG. 17, FIG. 18A, FIG. 18B, FIG. 19, and FIG. 20 show the image forming apparatus 100 that can further shorten the preheating time by subdividing the image width of the recording material P into two (plural). While explaining.

  FIG. 17 is a diagram for explaining the image width detection process of the image width detection unit 21 corresponding to the subdivision of the image width. 18A and 18B are flowcharts of lighting ratio control corresponding to subdivision of the image width. The flowcharts shown in FIGS. 18A and 18B are also applicable to the image forming apparatus 100 according to the third embodiment. FIG. 19 is a diagram showing the relationship between the upper threshold temperature and the lower threshold temperature according to the image width.

In the image width detection unit 21, when the toner amount information received by the video controller 20 is an A4 size width 210 mm shown in FIG. 17 and an image width (image area) 190 mm symmetrical with respect to the center of the A4 size width, The margin (non-image area) is E1. The maximum toner loading amount at E1 <0.1 mg / cm ²
And the maximum toner loading amount in E2 ≧ 0.1 mg / cm ² (2)
When the condition is satisfied, it is determined that the image width D is detected to be 190 mm.

  That is, the image width detection unit 21 detects two image widths (multiple detections). Here, E2 is a region obtained by subtracting E1 from E described in the first embodiment.

  In the present embodiment, a case will be described in which an image width of 190 mm is detected after n = 101 sheets during printing of n = 100 sheets after 100 sheets of image width of 180 mm are detected.

  Hereinafter, the flowchart of the lighting ratio control shown in FIGS. 18A and 18B will be described in detail in the case where toner images are continuously formed on a plurality of sheets.

  In response to the print job, continuous printing of n sheets is started (S11). In the present embodiment, n = 105 as in the first embodiment. Similarly, in Example 3 described later, n = 105. In this embodiment, the fixing device B continuously prints a color image with an image width = 180 mm satisfying the formula (1) from room temperature to n = 1 to n = 100, and then n = 101. A color image satisfying (2) is printed. In other words, the controller 23 prints the n = 100th sheet (preceding (previous) recording material) while the n = 101th sheet (following recording material) and the image width detecting unit 21 sets the “image width”. = 190 mm "toner amount information is detected.

  Hereinafter, processes from n = 1 are sequentially described.

  From n = 1 to n = 99, (S12) → (S12a) → (S12b) → (S12c) → (S13c) → (S14c) → (S15) → (S16) → (S17) is repeated. . In (S12c), since the (n + 1) th image width = 180 mm, the upper threshold temperature is set to −8 ° C. and the lower threshold temperature is set to −24 ° C. according to FIG. In (S15), the lighting ratio is controlled with a setting change threshold time of 1.2 seconds.

  Next, the case of n = 100th sheet will be described.

  Since the n = 100th image has an image width of 180 mm and the n = 101th image has an image width of 190 mm, (S12) → (S12a) → (S12b) → (S12c) → (S13c) → (S4) → ( The process proceeds in the order of S15).

  In the preheating mode of (S4), at the start of preheating of (S4a), the lighting ratio setting is switched according to the power value for fixing the n = 100th toner image of (S4b). Since the power value detected by the power detection unit 25 when fixing the n = 100th toner image is 531 W, the lighting ratio is set to -10 steps based on the table of FIG. 16, that is, the heat generation in the non-passing area. Switch 10 steps to increase the amount. Further, in (S4c), according to FIG. 19, the condition corresponding to the image width of 190 mm, specifically, the upper threshold temperature is updated to 3 ° C. and the lower threshold temperature is updated to −10 ° C.

  Thereafter, in (S4d), the setting change threshold time is shortened to 0.3 seconds. In (S4e), as soon as it converges to the edge target temperature range corresponding to the next image width, in (S4f), the edge preheating of the sheet is performed. finish.

  When the preheating mode of (S4) ends, the setting change threshold time is returned to 1.2 seconds in (S15). Thereafter, the number of sheets is updated through (S16) and (S17).

  Next, the case of n = 101st sheet to n = 105th sheet will be described.

  Since the nth image width is 190 mm, (S12) → (S12a) → (S12b) → (S12c) → (S12d) → (S13d) → (S14d) → (S15) → (S16) → (S17) ) Is repeated until the last page n = 105th page.

  Since the image width is 190 mm, in (S14d), the upper threshold temperature is 3 ° C. and the lower threshold temperature is −10 ° C. according to FIG. In (S15), the lighting ratio is controlled with a setting change threshold time of 1.2 seconds.

  FIG. 20 shows the lighting ratio setting, the setting change threshold time, and the temperature profile of the sub-thermistor 14 in the above-described lighting ratio control flowchart.

  As shown in FIG. 19, a monochrome text image is printed from the room temperature state under a condition corresponding to an image width of 180 mm, specifically, 100 sheets are printed continuously at an upper threshold temperature of −8 ° C. and a lower threshold temperature of −24 ° C. The lighting ratio setting of the heating element 4b2 has converged to 50%. Then, during printing of the n = 100th sheet, an image width of 190 mm is detected on the n = 101th sheet. Immediately after that, the edge preheating of the 101st sheet is started so that the temperature detected by the sub-thermistor 14 converges to the edge target temperature range corresponding to the image width of the 101st sheet.

  As described above, since the power value detected by the power detection unit 25 when fixing the toner image on the 100th sheet is 531 W, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is set according to FIG. -10 stages, that is, 10 stages are switched so as to increase the amount of heat generated in the non-passing area. That is, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is immediately switched from 50% at the 16th stage k to 100% at the 6th stage l.

  Next, the upper threshold temperature is updated to 3 ° C., the lower threshold temperature is updated to −10 ° C., and the setting change threshold time is shortened to 0.3 seconds, so that the lighting ratio setting is quickly changed from k → l → m → n. Switch. Thereby, the temperature detected by the sub-thermistor 14 can be converged to the end target temperature range. As a result, the time from the start of preheating to the end of preheating is 1.4 seconds, and printing can be continued without impairing productivity.

  As described above, the image forming apparatus 100 of the present embodiment can further shorten the preheating time compared to the first embodiment.

[Example 3]
Another example of the image forming apparatus 100 will be described. An image forming apparatus 100 that can further shorten the preheating time by subdividing the image width of the recording material P into three (plurality) will be described with reference to FIGS. 16, 18A, 18B, 19, and 21. To do.

  FIG. 21 is a diagram for explaining the image width detection processing of the image width detection unit 21 corresponding to the subdivision of the image width.

In the image width detection unit 21, when the toner amount information received by the video controller 20 is an A4 size width 210 mm shown in FIG. 21 and an image width (image area) 150 mm symmetrical to the center of the A4 size width, The margin (non-image area) is assumed to be E1 + E2 + E3. The maximum toner loading amount at E1 <0.1 mg / cm ²
And the maximum toner loading amount in E2 <0.1 mg / cm ²
And the maximum toner loading amount in E3 <0.1 mg / cm ² (3)
When the condition is satisfied, it is determined that the image width D is detected to be 150 mm.

  That is, the image width detection unit 21 detects three image widths (multiple detections). Here, E3 is a margin (non-image area) E4 in the second embodiment from an A4 size width 210 mm shown in the figure and a left-right symmetrical image width (image area) 150 mm with respect to the center of the A4 size width. This is an area obtained by subtracting the described margin E1 + E2.

  In the present embodiment, a case where an image width of 200 mm is detected after n = 101 sheets during printing of n = 100 sheets after detecting 100 sheets of an image width of 150 mm will be described.

  Hereinafter, a flowchart of the lighting ratio control according to the present embodiment will be described in detail along with a case where toner images are continuously formed on a plurality of sheets illustrated in FIGS. 18A and 18B.

  In response to the print job, continuous printing of n sheets is started (S11). In this embodiment, the fixing device B continuously prints a color image having an image width = 150 mm satisfying the equation (3) from the room temperature state to n = 1 sheet to n = 100 sheets, and then the equation (1 The image width satisfying (2) = 200 mm is printed. In other words, the control unit 23 determines that the image width detection unit 21 sets “image” on the n = 101th sheet (subsequent recording material) during printing of the n = 100th sheet (preceding (immediately preceding) recording material). It is determined that the toner amount information of “width = 200 mm” has been detected.

  Hereinafter, processes from n = 1 are sequentially described.

  From n = 1 to n = 99, (S12) → (S13) → (S14) → (S15) → (S16) → (S17) is repeated. Since the image width of the (n + 1) th sheet is 150 mm, in (S14), the upper threshold temperature is selected to be −24 ° C. and the lower threshold temperature is selected to be −40 ° C. according to FIG. In (S15), the lighting ratio is controlled with a setting change threshold time of 1.2 seconds.

  Next, the case of n = 100th sheet will be described.

  Since the n = 100th image has an image width of 150 mm and the n = 101th image has an image width of 200 mm, the process proceeds in the order of (S12) → (S13) → (S4) → (S15).

  In the preheating mode of (S4), at the start of preheating of (S4a), the lighting ratio setting is switched according to the power value for fixing the n = 100th toner image of (S4b). Since the power value detected by the power detection unit 25 when fixing the n = 100th toner image is 491 W, the lighting ratio setting of the sub-heating element 4b2 at the start of the preheating is set to -12 steps according to the table of FIG. In other words, 12 steps are switched so as to increase the amount of heat generated in the non-passing area. Further, in (S4c), the condition corresponding to the image width of 200 mm, specifically, the upper threshold temperature is updated to 18 ° C. and the lower threshold temperature is updated to 5 ° C.

  Thereafter, in (S4d), the setting change threshold time is shortened to 0.3 seconds. In (S4e), as soon as it converges to the edge target temperature range corresponding to the next image width, in (S4f), the edge preheating of the sheet is performed. finish.

  When the preheating mode of (S4) ends, the setting change threshold time is returned to 1.2 seconds in (S15). Thereafter, the number of sheets is updated through (S16) and (S17).

  Next, the case of n = 101st sheet to n = 105th sheet will be described.

  Since the nth image width = 200 mm, (S12) → (S12a) → (S12b) → (S12c) → (S12d) → (S14e) → (S15) → (S16) → (S17) is the last page Repeat until n = 105.

  In (S14e), since the image width is 200 mm, the upper threshold temperature is selected to be 18 ° C. and the lower threshold temperature is selected to be 5 ° C. according to FIG. In (S15), the lighting ratio is controlled every setting change threshold time 1.2 seconds.

  FIG. 22 shows the lighting ratio setting, the setting change threshold time, and the temperature profile of the sub-thermistor 14 in the above-described lighting ratio control flowchart.

  A monochrome text image from room temperature is printed on 100 sheets continuously under the conditions corresponding to the image width of 150 mm shown in FIG. 19, specifically, with the upper threshold temperature set at -24 ° C. and the lower threshold temperature set at -40 ° C. The lighting ratio setting of the heating element 4b2 converged to 35%. Then, during printing of the n = 100th sheet, it was detected that the image width of the n = 101th sheet was 200 mm. Immediately after that, the edge preheating of the 101st sheet is started so that the temperature detected by the sub-thermistor 14 converges to the edge target temperature range corresponding to the image width of the 101st sheet.

  As described above, since the power value detected by the power detection unit 25 when fixing the toner image on the 100th sheet is 491 W, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is set according to FIG. -12 stages, that is, 12 stages are switched so as to increase the amount of heat generated in the non-passing region. In other words, the lighting ratio setting of the sub-heating element 4b2 at the start of preheating is immediately switched from 19 of o to 7 of p.

  Next, the upper threshold temperature is updated to −24 ° C., the lower threshold temperature is updated to −40 ° C., and the setting change threshold time is shortened to 0.3 seconds, so that the lighting ratio setting is quickly changed from o → p → q → r. Switch to Thereby, the temperature detected by the sub-thermistor 14 can be converged to the end target temperature range. As a result, the time from the start of preheating to the end of preheating is 1.7 seconds, and while continuing to reduce power consumption compared to the second embodiment, printing can be continued without impairing productivity.

  FIG. 23 shows measurement results of time and power consumption required for preheating in Examples 1, 2, and 3, Experimental Example 1, and Comparative Examples 1 and 2.

  As described above, with respect to the image forming apparatus 100 of each embodiment, the effect in the case of 105 print jobs when the image width is detected to be 150 mm, 180 mm, 190 mm, and 200 mm has been described. Regardless of the detected image width, the number of sheets, and the recording material size, the above lighting ratio when the image width detection result of the succeeding recording material is wider than the image width detection result of the preceding (immediately preceding) recording material. By executing the control, the productivity can be improved as in the embodiments.

1 cylindrical film, 13 main thermistor, 14 sub thermistor,
4 Ceramic heater, 4a substrate, 4b1 main heating element, 4b2 sub heating element,
21 image width detection unit, 22 lighting ratio control unit, 23 control unit,
107 Endless belt, 108 Secondary transfer member P Recording material, Y Direction perpendicular to recording material conveyance direction X, t Unfixed toner image

Claims (6)

An image forming apparatus for forming an image on a recording material,
An image carrier;
A transfer member for transferring a toner image carried by the image carrier to a recording material;
A first heating element that reduces the amount of heat generation from the center in the direction orthogonal to the recording material conveyance direction toward the end, and a first heat generation amount that increases from the center in the direction orthogonal to the recording material conveyance direction toward the edge. A heating member having a second heating element and a substrate provided with the first and second heating elements;
A cylindrical fixing member that rotates while contacting the substrate and the inner peripheral surface, heats the recording material carrying the toner image, and fixes the toner image on the recording material by heating;
In an image forming apparatus having
Lighting ratio control means for controlling the lighting ratio of the first heating element and the second heating element at a constant period;
Image width detection means for detecting an image width in a direction orthogonal to the recording material conveyance direction of the toner image transferred from the image carrier to the recording material;
Power detection means for detecting power supplied to the first heating element and the second heating element;
Control means for setting a lighting period control period of the first heating element and the second heating element, and a lighting ratio setting of the second heating element;
Have
When continuously forming toner images on a plurality of recording materials, the control means has a wider image width of the toner image detected by the image width detection means than the recording material immediately before the toner image was formed. In this case, the lighting ratio control cycle is shortened, and the lighting ratio setting is switched according to the power detection result by the power detection means when fixing the toner image on the immediately preceding recording material. .   2. The image width detecting unit according to claim 1, wherein the image width detecting unit detects the image width in a direction orthogonal to the recording material conveyance direction based on whether or not a predetermined toner amount is present outside the image width. Image forming apparatus.   The image forming apparatus according to claim 2, wherein the image width detecting unit detects a plurality of the image widths.   The apparatus further includes a first temperature detection member that detects a temperature of a region through which the recording material passes with respect to the second heating element in a direction orthogonal to the recording material conveyance direction, and a region in which the recording material does not pass through. And a lighting ratio setting of the second heating element is set based on the detected temperatures of the first and second temperature detecting members. The image forming apparatus according to any one of claims 1 to 3.   When the toner width detected by the image width detection means is wider than the recording material immediately before the toner image is formed, the control means turns on when the toner image is fixed to the immediately preceding recording material. The image forming apparatus according to claim 1, wherein the ratio setting is switched so that the amount of heat generated at the end portion is increased.   When the toner image detected by the image width detecting means is wider than the recording material immediately before the toner image is formed immediately before the toner image is fixed on the immediately preceding recording material, 6. The image forming apparatus according to claim 5, wherein the heat generation amount of the second heating element is increased.