Image forming apparatus

Abstract

To provide a fixing device that can control a temperature rise to be within an allowable range and prevent a reduction in productivity.SOLUTION: A fixing device comprises: a fixing roller 31 that applies heat and pressure to a sheet to fix an image; a heating unit 37 that heats a part in a width direction of the fixing roller 31; and a control unit 61 that controls paper feed at the fixing roller 31. In executing a job to feed narrow width paper having a narrower width than a heating range of the heating unit 37, the paper feed at the fixing roller 31 has a normal mode for feeding paper according to a preset condition and a paper feed restriction mode for restricting a ratio of paper feed per unit time. When the normal mode is executed for a preset paper feed restriction time, the control unit 61 performs transition control of making a transition to the paper feed restriction mode. When a plurality of jobs to feed the narrow width paper are executed, the control unit changes the paper feed restriction time in the next job according to the paper feed time in the previous job in the transition control.SELECTED DRAWING: Figure 3

Description

Technical Field

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[0001] The present disclosure relates to an image forming apparatus that pressurizes paper to fix an image. The picture

Background Art

[0002] Conventionally, in a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, the toner image is fixed by pressurizing and heating the paper on which the unfixed toner image is formed. In the fixing device, a heater or the like is provided to heat the fixing member so as to maintain a desired temperature.

[0003] By the way, in an image forming apparatus, in order to meet various applications, it is configured to be able to form an image on papers of different sizes (widths). Among the papers that can pass through, the heating range of a heater or the like is set according to the largest-sized paper. Therefore, when passing a small-sized paper, a non-paper-passing portion that does not contact the paper occurs at the end of the fixing member. In the non-paper-passing portion, since it is heated without the temperature decreasing due to contact with the paper, the temperature may rise excessively, causing damage or melting of the fixing member. Therefore, in order to solve this problem, the paper passing is restricted (CPM down) or the image formation is temporarily stopped to suppress the temperature rise, but there is a problem that the productivity is thereby reduced. In response to such problems, an image heating device that prevents a decrease in productivity has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004] [[ID=2,9]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] ​Conventional image heating devices include an image heating means that heats an image on a recording material (paper) at a nip section, and a cooling means that cools the area outside the recording material transport region of the image heating means by blowing air. When the width of the recording material is within a predetermined range, image formation is performed with a cooling operation. When the width of the recording material is less than or equal to the predetermined width, image formation (CPM down) is performed without a cooling operation, reducing the number of recording materials that pass through the nip section per unit time.

[0006] The image heating device described above has the problem of reduced productivity because it constantly performs CPM reduction on recording materials of a certain width or less.

[0007] This disclosure was made to solve the above-mentioned problems, and it is possible to keep the temperature rise within an acceptable range and prevent a decrease in productivity. The picture The objective is to provide an image forming apparatus. [Means for solving the problem]

[0008] Regarding this disclosure Image forming apparatus It includes a fixing member that heats and pressurizes the paper to fix the image. Image forming apparatus The device comprises a heating unit that heats a portion of the fixing member in the width direction, and a control unit that controls the feeding of paper through the fixing member. When performing a job to feed narrow paper, which is narrower than the heating range of the heating unit, the device has a normal mode in which paper is fed under preset conditions, and a paper-feeding restriction mode that limits the rate of paper fed per unit time. The control unit performs transition control to switch to the paper-feeding restriction mode when the normal mode has been executed for a preset paper-feeding restriction time. The aforementioned job is a job that is received from the user as an instruction to perform image formation, and when a sheet of paper with a width greater than or equal to the heating range of the heating unit is defined as wide paper, and a job in which narrow paper and wide paper are mixed is defined as a mixed job, When executing multiple jobs that feed the aforementioned narrow paper, the transition control will: The time interval between the completion of one job and the start of the next job. Accordingly, the paper pass time limit for the next job will be changed. The paper feeding time for the wide paper in the mixed-load job is considered as the intermittent time, and the paper feeding limit time is determined accordingly. It is characterized by the following.

[0009] Regarding this disclosure Image forming apparatus In the transition control, the paper passing time for the previous job may be subtracted from the paper passing limit time, and this subtraction may be used as the paper passing limit time for the next job.

[0010] Regarding this disclosure Image forming apparatus In the transition control, if the previous job has finished in the normal mode, the paper passing time of multiple previous jobs executed in the normal mode may be accumulated, and the accumulated paper passing time may be subtracted from the paper passing limit time.

[0012] Regarding this disclosure Image forming apparatus In the transition control, if the intermittent time is less than a preset reset time, the paper passing time for the previous job may be subtracted from the paper passing limit time. If the intermittent time is equal to or greater than the reset time, the paper passing time for the previous job may be ignored when determining the paper passing limit time.

[0014] Regarding this disclosure Image forming apparatus In the aforementioned paper feed restriction mode, the configuration may be such that the spacing between sheets of paper being fed continuously is controlled.

[0015] Regarding this disclosure Image forming apparatus In the aforementioned paper feed restriction mode, the configuration may be such that the transport speed of the paper being fed is controlled. [Effects of the Invention]

[0017] This configuration allows for controlling the timing of CPM down control based on the previous job, thereby keeping the temperature rise within acceptable limits and preventing a decrease in productivity. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic side view of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] This is a schematic side view showing an enlarged view of the vicinity of the fixing device in Figure 1. [Figure 3] This is a schematic diagram showing the general configuration of an image forming apparatus. [Figure 4] This is a schematic diagram illustrating the relationship between the heating range of the heating element on the fixing roller and the paper. [Figure 5] This is an explanatory diagram showing an example of transition control (part 1). [Figure 6] It is an explanatory diagram showing an example of transition control (Part 2). [Figure 7] It is an explanatory diagram showing an example of transition control (Part 3). [Figure 8] It is an explanatory diagram showing an example of transition control (Part 4). [Figure 9] It is an explanatory diagram showing an example of transition control (Part 5). [Figure 10] It is a flowchart showing a processing flow when feeding narrow-width paper in the image forming apparatus according to an embodiment of the present disclosure.

Mode for Carrying Out the Invention

[0019] Hereinafter, the image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

[0020] FIG. 1 is a schematic side view of an image forming apparatus according to an embodiment of the present disclosure.

[0021] An image forming apparatus 1 according to an embodiment of the present disclosure includes a main body that performs image formation, a document reading unit 44 and a document conveyance unit 45 provided at the upper part, and a paper feeding device 50 provided at the lower part. The paper feeding device 50 is composed of a device main body 52 and a paper feeding cassette 51 inserted into the device main body 52.

[0022] The document reading unit 44 has a document placement table 43 on which documents are placed provided on the upper surface, reads an image of the document on the document placement table 43, creates image data, and transmits it to the image forming apparatus 1. The document conveyance unit 45 automatically conveys the document onto the document placement table 43. Further, the document conveyance unit 45 is rotatably attached to the image forming apparatus 1, and by rotating it to open the upper part of the document placement table 43, the document can be placed manually.

[0023] The main body of the image forming apparatus 1 is equipped with an exposure unit 11, a developing unit 12, a photoreceptor drum 13, a cleaning unit 14, a charger 15, a transfer unit 20, a fixing unit 17, a paper output tray 39, and a paper transport path R1. It forms multi-color and monochrome images on a predetermined sheet of paper according to image data transmitted from an external source or from the document reading unit 44.

[0024] The image data handled by the image forming apparatus 1 corresponds to a color image using the colors black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, four of each of the developing apparatus 12, photoreceptor drum 13, charger 15, and cleaning apparatus 14 are provided to form four types of latent images corresponding to each color, and are set to black, cyan, magenta, and yellow respectively, and these constitute four image stations Pa, Pb, Pc, and Pd.

[0025] The photoreceptor drum 13 is positioned approximately in the center in the height direction of the image forming apparatus 1. The charger 15 uniformly charges the surface (circumferential surface) of the photoreceptor drum 13 to a predetermined potential. The exposure apparatus 11 exposes the surface of the photoreceptor drum 13 to form an electrostatic latent image. The developing apparatus 12 develops the electrostatic latent image on the surface of the photoreceptor drum 13 to form a toner image on the surface of the photoreceptor drum 13. Through the above series of operations, toner images of each color are formed on the surface of each photoreceptor drum 13. The cleaning apparatus 14 removes and recovers residual toner from the surface of the photoreceptor drum 13 after development and image transfer.

[0026] The transfer unit 20 comprises a transfer drive roller 22, a transfer driven roller 23, and an intermediate transfer belt 21. The intermediate transfer belt 21 is suspended from the transfer drive roller 22 and the transfer driven roller 23, which are rotated by a connected drive source, and moves together with the transfer driven roller 23 in accordance with the rotation of the transfer drive roller 22. The intermediate transfer belt 21 moves in a circular motion in the direction of arrow C, and residual toner is removed and collected by the intermediate transfer belt cleaning device 25. The toner images of each color formed on the surface of each photoreceptor drum 13 are sequentially transferred and superimposed, forming a color toner image on the surface of the intermediate transfer belt 21.

[0027] The image forming apparatus 1 further comprises a secondary transfer apparatus 26 including a transfer roller 26a. The transfer roller 26a has a transfer nip area formed between it and the intermediate transfer belt 21, and transports the paper that has been transported through the paper transport path S by gripping it in the transfer nip area. As the paper passes through the transfer nip area, the toner image on the surface of the intermediate transfer belt 21 is transferred to it.

[0028] The image forming apparatus 1 performs image formation using paper stored in the paper feed cassette 51. The paper feed device 50 is located below the exposure device 11. The output tray 39 is located below the document reading unit 44 and is a tray for placing the paper with the image formed on it.

[0029] The paper is drawn out of the paper cassette 51 by the paper feed roller 33 and supplied to the S-shaped paper transport path R1. Further along the paper transport path R1 are the transport roller 35, registration roller 34, secondary transfer device 26, fixing device 17, and paper discharge roller 36.

[0030] The registration roller 34 temporarily holds the paper being transported from the paper feed cassette 51 and transports the paper to the transfer roller 26a at the timing when the leading edge of the toner image on the photoreceptor drum 13 aligns with the leading edge of the paper. The transport roller 35 is a small roller that assists in accelerating the transport of the paper.

[0031] The fuser unit 17 receives paper on which an unfixed toner image has formed, passes the paper between a fuser roller 31 (an example of a fuser member) and a pressure roller 32, and heats and pressurizes the paper to fix the toner image on the paper. After fixing, the paper is discharged onto the paper output tray 39 by the paper output roller 36. In this embodiment, a heating unit 37 is located inside the fuser roller 31, and a temperature sensing unit 38 is located outside the fuser roller 31. The fuser unit 17 will be described in detail with reference to Figure 2, which will be described later.

[0032] Furthermore, when image formation is to be performed on the back side of the paper as well as the front side, the paper is transported in the reverse direction from the paper output roller 36 to the reversal path Rr to reverse the front and back sides of the paper, and the paper is guided back to the registration roller 34, where image formation is performed on the back side in the same way as on the front side, and the paper is then delivered to the paper output tray 39.

[0033] Figure 2 is a schematic side view showing an enlarged view of the vicinity of the fixing device in Figure 1.

[0034] As described above, the fixing device 17 includes a fixing roller 31, a pressure roller 32, a heating unit 37, and a temperature detection unit 38. The heating unit 37 is a heater lamp or heating element that generates heat when power is supplied. The timing of heating in the heating unit 37 can be controlled according to the detection result from the temperature detection unit 38. The temperature detection unit 38 is, for example, a non-contact type temperature sensor.

[0035] Figure 3 is a schematic diagram showing the general configuration of an image forming apparatus.

[0036] The image forming apparatus 1 further includes a control unit 61 and a receiving unit 62. Although Figure 3 shows only a portion of the image forming apparatus 1, it may also include other components. The control unit 61 controls the paper feeding at the fixing roller 31. The receiving unit 62 receives instructions from the user to execute an image forming (job). In a job received from a user, the image to be formed and the corresponding paper type may be associated and accepted. In addition, a job may accept image forming for multiple sheets of paper at once.

[0037] Next, the relationship between the fixing roller 31 and the paper width will be explained with reference to Figure 4.

[0038] Figure 4 is a schematic diagram illustrating the relationship between the heating range of the heating section relative to the fixing roller and the paper.

[0039] Figure 4 shows the relative positions of the fixing roller 31, heating unit 37, temperature sensing unit 38, and paper in the width direction W. In this embodiment, the heating unit 37 consists of a main heater 37a and a sub-heater 37b. The main heater 37a has a heating element (main heating element HE1) in the center in the width direction W. The sub-heater 37b has heating elements (sub-heating elements HE2) at both ends in the width direction W, and the sub-heating elements HE2 slightly overlap with the ends of the main heating element HE1 in the width direction W.

[0040] In this embodiment, the temperature detection unit 38 is composed of a main detection unit 38a, a sub-detection unit 38b, and a non-feeding paper detection unit 38c. The main detection unit 38a is located approximately in the center in the width direction W, corresponding to the main heating unit HE1. The sub-detection unit is located closer to the edge in the width direction W, corresponding to the sub-heating unit HE2. The non-feeding paper detection unit 38c is located at the edge in the width direction W, corresponding to the edge of the sub-heating unit HE2. For explanatory purposes below, the range in the width direction W corresponding to the main heating unit HE1 may be referred to as the heating range KA.

[0041] The image forming apparatus 1 is capable of forming images on multiple types of paper with different sizes (widths). In the image forming apparatus 1, the paper is fed through such that the center of the fixing roller 31 in the width direction W and the center of the paper in the width direction W approximately coincide. Figure 4 shows examples of image-formable paper, namely the first paper P1 (an example of wide paper), the second paper P2 (an example of wide paper), and the third paper P3 (an example of narrow paper). The first paper P1 is wider than the main heating element HE1 (heating range KA), and its edges overlap the sub-heating element HE2. In other words, by operating the main heater 37a and the sub-heater 37b, the portion corresponding to the first paper P1 can be heated. The second paper P2 is approximately the same width as the main heating element HE1 (heating range KA). In other words, by operating the main heater 37a, the portion corresponding to the second paper P2 can be heated. The third paper P3 is narrower than the main heating element HE1 (heating range KA). By operating the main heater 37a, a wider area than the third sheet of paper P3 is heated. As a result, when the third sheet of paper P3 is fed continuously, the temperature of the fixing roller 31 may rise excessively in the non-feeding area outside the third sheet of paper P3.

[0042] Therefore, the image forming apparatus 1 suppresses temperature rise by limiting paper feeding (CPM reduction). Specifically, the image forming apparatus 1 is equipped with a normal mode in which paper is fed under preset conditions when performing a job that feeds narrow paper with a width narrower than the heating range KA, and a paper feeding restriction mode that limits the rate of paper fed per unit time. In the paper feeding restriction mode, the spacing between sheets of paper fed consecutively is controlled to be wider than in the normal mode. When the spacing between sheets of paper is wider, the time until the next sheet of paper is fed is longer, so the unevenness in the temperature distribution at the fuser roller 31 is eliminated. In this way, CPM reduction can be easily performed by controlling the spacing between sheets of paper. The spacing between sheets of paper can be controlled by adjusting the timing of pulling the paper out of the paper feed cassette 51 or by adjusting the timing of transporting the paper from the registration roller 34. In addition, in the paper feeding restriction mode, the transport speed of the paper being fed may be controlled to be slower than in the normal mode, not limited to the method described above.

[0043] Next, the transition control for switching between normal mode and paper feed restriction mode will be explained with reference to Figures 5 to 9.

[0044] Figure 5 is an explanatory diagram showing an example of transition control (part 1).

[0045] Figure 5 and Figures 6 through 9, described later, show the operation of the image forming apparatus 1 over time. For explanatory purposes, the operation of the image forming apparatus 1 in normal mode will be referred to as "normal operation," and the operation of the image forming apparatus 1 in paper-feed-restricted mode will be referred to as "paper-feed-restricted operation." In addition, the operation of the image forming apparatus 1 that accommodates the feeding of wide paper will be referred to as "wide operation."

[0046] In this embodiment, when executing a job that feeds narrow paper under normal circumstances, the job is started in normal mode. When the paper feeding time in normal operation (first normal operation TD1) reaches the paper feeding limit time ST, the system switches to paper feeding limit mode, and thereafter, the paper feeding limit operation (first paper feeding limit operation SD1) is performed. In this embodiment, the paper feeding limit time ST is set to 65 seconds, but it is not limited to this and may be changed as appropriate. The paper feeding time can be appropriately calculated from a preset value according to the size (type) of the paper. In the transition control, the paper feeding time in the job is counted and subtracted from the paper feeding limit time ST, and when the paper feeding limit time ST becomes 0, the system switches to paper feeding limit mode. In this way, the timing of switching to paper feeding limit mode can be easily controlled by a simple calculation.

[0047] Figure 6 is an explanatory diagram showing an example of transition control (part 2).

[0048] In the image forming apparatus 1, a single job may specify a mix of narrow and wide paper to be fed through, and such a job containing a mix of narrow and wide paper is called a mixed-load job. In the transition control, the period from the end of one job to the start of the next is defined as the intermittent time. In a mixed-load job, the feeding time of the wide paper is considered an intermittent time, and the feeding limit time ST is determined accordingly. When feeding wide paper, no non-feeding areas occur within the heating range of the fixing roller 31, and the temperature rise is suppressed. Therefore, the feeding time can be treated the same as an intermittent time, allowing for more appropriate control.

[0049] Figure 6 shows the operation of the image forming apparatus 1 in a mixed-load job. In the job shown in Figure 6, narrow paper and wide paper are fed alternately. Specifically, at the start of the job, narrow paper is fed (second normal operation TD2) in normal mode, followed by wide paper (first wide operation ND1). After that, narrow paper and wide paper are fed alternately, in the order of third normal operation TD3, second wide operation ND2, fourth normal operation TD4, third wide operation ND3, and fifth normal operation TD5. At this time, the paper feeding time for the second normal operation TD2, third normal operation TD3, fourth normal operation TD4, and fifth normal operation TD5 is accumulated, and if the accumulated time exceeds the paper feeding limit time ST, the apparatus switches to paper feeding limit mode, and after the fifth normal operation TD5, a paper feeding limit operation (second paper feeding limit operation SD2) is performed. In other words, when feeding multiple narrow sheets of paper, the CPM (Coefficient of Performance) is reduced during the 5th normal operation TD5, and the 2nd paper feeding restriction operation SD2 is performed.

[0050] As mentioned above, if paper is repeatedly fed in normal mode without CPM reduction, there is a concern about temperature rise. By accumulating the paper feeding time, the timing of switching to paper feeding restriction mode can be brought forward, thereby suppressing the temperature rise.

[0051] Next, we will explain the case where wide paper is fed after switching to paper feed restriction mode in a mixed load job, with reference to Figures 7 and 8.

[0052] Figure 7 is an explanatory diagram showing an example of transition control (part 3), and Figure 8 is an explanatory diagram showing an example of transition control (part 4).

[0053] In Figure 7, similar to the example shown in Figure 5, normal operation (6th normal operation TD6) is performed until the paper feeding limit time ST is reached, then the system switches to paper feeding restriction mode and performs paper feeding restriction operation (3rd paper feeding restriction operation SD3). After the 3rd paper feeding restriction operation SD3, wide paper feeding (4th wide paper operation ND4) is performed. Here, if the paper feeding time (1st intermittent time KT1) of the 4th wide paper operation ND4 is shorter than the preset reset time, the paper feeding restriction mode is maintained and the 4th paper feeding restriction operation SD4 is performed. In this embodiment, the reset time is set to 60 seconds, but it is not limited to this and may be changed as appropriate.

[0054] Figure 8 is the same as the example shown in Figure 7, in that after normal operation (7th normal operation TD7), the system transitions to paper feed restriction mode, performs paper feed restriction operation (5th paper feed restriction operation SD5), and then performs wide paper feed (5th wide paper operation ND5). Figure 8 shows the case where the paper feed time (2nd intermittent time KT2) of the 5th wide paper operation ND5 is longer than the preset reset time. In this case, the system ignores the paper feed time up to that point, transitions to normal mode, and performs the 8th normal operation TD8.

[0055] As described above, in transition control, when the intermittent time is less than the reset time, the paper passing time for the job is subtracted from the paper passing limit time ST. On the other hand, when the intermittent time is equal to or greater than the reset time, the paper passing time for the job is ignored when determining the paper passing limit time ST. In other words, the paper passing limit time ST is reset to its initially set value. Thus, if the intermittent time is longer than the predetermined reset time, it can be determined that the temperature rise is sufficiently suppressed, and by resetting the subtraction of the paper passing limit time ST, more appropriate control can be performed.

[0056] Figures 7 and 8 show the case where the period during which wide paper is being fed is considered an intermittent time, but the process is not limited to this. The same processing can be performed even if the fourth wide operation ND4 and the fifth wide operation ND5 are replaced with a period during which no paper is being fed to the fuser roller 31. In other words, Figure 7 corresponds to the case where the third paper feeding restriction operation SD3 is performed as the previous job, followed by a first intermittent time KT1 during which no paper is being fed, and then the fourth paper feeding restriction operation SD4 is performed as the next job. Similarly, Figure 8 corresponds to the case where the fifth paper feeding restriction operation SD5 is performed as the previous job, followed by a second intermittent time KT2 during which no paper is being fed, and then the eighth normal operation TD8 is performed as the next job.

[0057] Figure 9 is an explanatory diagram showing an example of transition control (part 5).

[0058] Figure 9 shows the case where a time interval is left after the previous job is performed before the next job is performed. Specifically, after a short normal operation (normal operation 9 TD9), a third intermittent time KT3 is left, and then normal operation (normal operation 10 TD10) is started again. At this time, the paper passing time in normal operation 9 TD9 is subtracted from the paper passing limit time ST, and then the paper passing time in normal operation 10 TD10 is subtracted from the paper passing limit time ST. When the paper passing limit time ST becomes 0 after the subtraction process, the system switches to paper passing limit mode and performs a paper passing limit operation (paper passing limit operation 6 SD6).

[0059] For example, if the paper feeding time in the 9th normal operation TD9 is set to 10 seconds and the paper feeding limit time ST is set to 65 seconds, the 6th paper feeding limit operation SD6 will be executed when the paper feeding time in the 10th normal operation TD10 exceeds 55 seconds. In this way, by controlling the timing of CPM down control according to the previous job, the temperature rise can be kept within an acceptable range, and a decrease in productivity can be prevented.

[0060] As shown in Figure 9, if wide paper is fed (sixth wide paper operation ND6) during the third intermittent time KT3, the paper feeding time for the sixth wide paper operation ND6 is considered an intermittent time and is not reflected in the deduction of the paper feeding limit time ST.

[0061] Next, the processing flow for feeding narrow paper into the image forming apparatus 1 will be explained with reference to Figure 10.

[0062] Figure 10 is a flowchart showing the processing flow when feeding narrow paper in an image forming apparatus according to an embodiment of the present disclosure.

[0063] In step S01, the reception unit 62 accepts job requests from users.

[0064] In step S02, the control unit 61 determines whether the current state is paper feed restriction mode. If the result is that it is paper feed restriction mode (step S02: Yes), proceed to step S03. On the other hand, if it is not paper feed restriction mode (step S02: No), proceed to step S05.

[0065] In step S03, the control unit 61 determines whether the intermittent time exceeds the reset time. Specifically, if the intermittent time exceeds the reset time, it corresponds to the example shown in Figure 8, and if the intermittent time does not exceed the reset time, it corresponds to the example shown in Figure 7. If the intermittent time exceeds the reset time (step S03: Yes), the process proceeds to step S04. On the other hand, if the intermittent time does not exceed the reset time (step S03: No), the process proceeds to step S08.

[0066] In step S04, the control unit 61 resets the accumulated time and switches to normal mode.

[0067] In step S05, the control unit 61 causes printing to be performed in normal mode. Here, the paper feeding time is counted as the cumulative time. If printing in normal mode is repeated without resetting the cumulative time, the accumulated paper feeding time is used as the cumulative time.

[0068] In step S06, the control unit 61 determines whether the accumulated time exceeds the paper feed limit time. If the accumulated time exceeds the paper feed limit time (step S06: Yes), the process proceeds to step S07. On the other hand, if the accumulated time does not exceed the paper feed limit time (step S06: No), the process proceeds to step S09.

[0069] In step S07, the control unit 61 switches to paper feed restriction mode.

[0070] In step S08, the control unit 61 causes printing to be performed in paper feed restriction mode.

[0071] In step S09, the control unit 61 determines whether the job has finished. If the job has finished (step S09: Yes), the process terminates. If the job has not finished (step S09: No), the process returns to step S02.

[0072] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of Symbols]

[0073] 1. Image forming apparatus 17 Fixing device 31. Fixing roller (an example of a fixing member) 37 Heating section 38 Temperature detection unit 61 Control Unit 62 Reception Department KA heating range W (width direction)

Claims

1. An image forming apparatus equipped with a fixing member that heats and pressurizes paper to fix an image, A heating section that heats a portion of the fixing member in the width direction, The system includes a control unit that controls the feeding of paper through the fixing member, In the paper feeding operation of the fixing member, when performing a job that feeds narrow paper with a width narrower than the heating range of the heating section, there is a normal mode in which paper is fed under preset conditions and a paper feeding restriction mode that limits the rate of paper fed per unit time. The control unit performs transition control to switch to the paper-feeding restriction mode when the normal mode has been executed for a preset paper-feeding time limit. The aforementioned job is a job that is received from the user as an instruction to perform image formation, and when a sheet of paper with a width greater than or equal to the heating range of the heating unit is defined as wide paper, and a job in which narrow paper and wide paper are mixed is defined as a mixed job, When multiple jobs are executed that feed the narrow paper, the transition control changes the paper feeding limit time for the next job according to the intermittent time between the end of the previous job and the start of the next job, and determines the paper feeding limit time by considering the paper feeding time of the wide paper in the mixed-load job as the intermittent time. An image forming apparatus characterized by the following.

2. An image forming apparatus according to claim 1, In the transition control described above, the paper passing time for the previous job is subtracted from the paper passing limit time to determine the paper passing limit time for the next job. An image forming apparatus characterized by the following.

3. An image forming apparatus according to claim 2, In the transition control described above, if the previous job has finished in the normal mode, the paper passing times of multiple previous jobs executed in the normal mode are accumulated, and the accumulated paper passing time is subtracted from the paper passing limit time. An image forming apparatus characterized by the following.

4. An image forming apparatus according to any one of claims 1 to 3, In the transition control described above, if the intermittent time is less than a preset reset time, the paper passing time in the previous job is subtracted from the paper passing limit time, and if the intermittent time is equal to or greater than the reset time, the paper passing time in the previous job is ignored when determining the paper passing limit time. An image forming apparatus characterized by the following.

5. An image forming apparatus according to claim 1, In the aforementioned paper feed restriction mode, the spacing between sheets of paper being fed consecutively is controlled. An image forming apparatus characterized by the following.

6. An image forming apparatus according to claim 1, In the aforementioned paper feed restriction mode, the transport speed of the paper being fed is controlled. An image forming apparatus characterized by the following.

Images