Image forming apparatus

Abstract

To sufficiently reduce an increase in temperature in an image forming apparatus.SOLUTION: During the execution of a continuous printing mode for continuously performing printing operations on a plurality of sheets P, when a detected temperature of an in-apparatus temperature sensor 80 (temperature detection means) becomes equal to or more than a first execution temperature T1, the continuous printing mode is switched to an intermittent printing mode for alternately repeating operations to print a predetermined number of prints and stop of printing operations for a predetermined time, and when the detected temperature of the in-apparatus temperature sensor 80 becomes equal to or less than a first cancellation temperature T3 lower than the first execution temperature T1, the execution of the intermittent printing mode is cancelled and switched to the continuous printing mode. In the intermittent printing mode, when the detection temperature of the in-apparatus temperature sensor 80 does not decrease to the first cancellation temperature T3 even after the lapse of the predetermined time M1 from the start of execution of the intermittent printing mode, heating of a fixing device 20 by a heater 25 is stopped.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] This invention relates to an image forming apparatus such as a copier, a printer, a facsimile machine, or a multi-function machine thereof.

Background Art

[0002] Conventionally, in an image forming apparatus such as a copier or a printer, in order to prevent a problem that the temperature inside the image forming apparatus rises above a predetermined value during continuous printing, a technology of executing an intermittent printing mode in which printing operations and printing operation stops are alternately repeated is known (see, for example, Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0003] Conventional technologies may not be able to sufficiently reduce the temperature rise inside the image forming apparatus even when the intermittent printing mode is executed. Therefore, problems such as toner aggregation or melting in the image forming unit due to the temperature rise, resulting in a decrease in the quality of the printed image, or a malfunction of the image forming unit have occurred.

[0004] This invention has been made to solve the above problems, and an object thereof is to provide an image forming apparatus capable of sufficiently reducing the temperature rise inside the image forming apparatus.

Means for Solving the Problems

[0005] The image forming apparatus in this invention comprises a fixing device that is heated by a heating means to fix a toner image to the surface of a sheet, and a temperature detection means for detecting the internal temperature of the main body of the image forming apparatus. During the execution of a continuous printing mode in which printing operations are performed on multiple sheets in succession, when the temperature detected by the temperature detection means reaches or exceeds a first execution temperature, the apparatus switches to an intermittent printing mode in which a predetermined number of printing operations and a predetermined period of time of print stoppage are alternately repeated. When the temperature detected by the temperature detection means falls below a first release temperature, which is lower than the first execution temperature, the intermittent printing mode is deactivated and the apparatus switches back to the continuous printing mode. In the intermittent printing mode, if the temperature detected by the temperature detection means does not fall to the first release temperature even after a predetermined time has elapsed since the start of the intermittent printing mode, the heating of the fixing device by the heating means is stopped. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide an image forming apparatus that can sufficiently reduce the temperature rise inside the image forming apparatus. [Brief explanation of the drawing]

[0007] [Figure 1] This is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of the fixing device. [Figure 3] This graph shows an example of how the print mode changes when continuous printing mode is started. [Figure 4] This graph shows an example of the relationship between the change in the set fixing temperature and the actual change in fixing temperature when continuous printing mode is started. [Figure 5] This flowchart shows an example of controlling the continuous printing mode. [Figure 6] The flowchart shows an example of controlling the continuous printing mode. [Figure 7] This flowchart shows the control sequence that follows Figure 6. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments for carrying out this invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be simplified or omitted as appropriate.

[0009] First, Figure 1 will explain the overall configuration and operation of the image forming apparatus 1. In Figure 1, 1 is a copier as an image forming apparatus, 2 is a document reading unit that optically reads image information from the original document D, and 3 is an exposure unit that irradiates exposure light L onto the photoreceptor drum 5 based on the image information read by the document reading unit 2. Furthermore, 4 represents the image-forming unit that forms a toner image on the surface of the photoreceptor drum 5, which acts as a photoreceptor; 5 represents the photoreceptor drum, which acts as a photoreceptor (image carrier); 6 represents the charging device that charges the surface of the photoreceptor drum 5; 7 represents the developing device that develops the latent image formed on the photoreceptor drum 5 to form a toner image (image); 8 represents the cleaning device that removes any untransferred toner remaining on the photoreceptor drum 5; and 9 represents the transfer device (transfer roller) that transfers the toner image formed on the photoreceptor drum 5 to the sheet P. The image-forming unit 4 consists of the photoreceptor drum 5, the charging device 6, the developing device 7, the cleaning device 8, the transfer device 9, and so on.

[0010] Furthermore, 10 is a document transport unit that transports the set document D to the document reading unit 2, 12 is a paper feed unit (paper feed cassette) in which a sheet P such as paper is stored, 20 is a fixing device that heats the toner image (unfixed image) on the sheet P and fixes it to the sheet P, and 45 is a timing roller (regist roller) that transports the sheet P toward the transfer device 9 (transfer nip). Furthermore, 31 is an exhaust duct for guiding the hot air inside the image forming apparatus 1 to the outside, 32 is an exhaust filter installed at exhaust port B of the exhaust duct 31, and 33 is an exhaust fan in the exhaust duct 31 that generates airflow from inside the apparatus to outside (exhaust port B). By discharging the hot air inside the image forming apparatus 1 to the outside via the exhaust duct 31, the temperature rise inside the image forming apparatus 1 is reduced. The exhaust filter 32 is used to capture ozone and UFP (particulate matter) contained in the air discharged from inside the apparatus. Furthermore, 80 indicates an internal temperature sensor (temperature sensor) as a temperature detection means for detecting the internal temperature of the image forming apparatus body 1, and 90 indicates an operation display panel as a display unit for displaying information related to the printing operation (image forming operation) and for performing operations.

[0011] Referring to Figure 1, the normal operation of the image forming apparatus during image formation will be explained. First, the original document D is transported from the document table in the direction of the arrow in the diagram by the transport rollers of the document transport unit 10 and passes over the document reading unit 2. At this time, the image information of the original document D passing over it is optically read by the document reading unit 2. The optical image information read by the document reading unit 2 is then converted into an electrical signal and transmitted to the exposure unit 3 (writing device). The exposure unit 3 then emits exposure light L (laser light) based on the image information in the electrical signal, directed towards the photosensitive drum 5.

[0012] Meanwhile, the photoreceptor drum 5, acting as a photoreceptor, rotates clockwise as shown in Figure 1. After a predetermined image formation process (charging, exposure, and development), an image (toner image) corresponding to the image information is formed on the photoreceptor drum 5. Subsequently, the image formed on the photoreceptor drum 5 is transferred to the sheet P, which is transported by the timing roller 45, at a position opposite the transfer device 9 (transfer nip).

[0013] More specifically, the photoreceptor drum 5 rotates clockwise as shown in Figure 1. First, the surface of the photoreceptor drum 5 is uniformly charged at the position opposite the charging device 6 (this is the charging process). In this way, a charge potential is formed on the photoreceptor drum 5. Subsequently, the surface of the charged photoreceptor drum 5 reaches the irradiation position of the exposure light L. Then, an electrostatic latent image based on the image information read by the document reading unit 2 is formed on the surface of the photoreceptor drum 5 (this is the exposure process). Subsequently, the surface of the photoreceptor drum 5, on which the electrostatic latent image has formed, reaches a position opposite the developing unit 7 (which contains the toner). Then, toner is supplied from the developing unit 7 onto the photoreceptor drum 5, and the latent image on the photoreceptor drum 5 is developed (this is the developing process). Subsequently, the surface of the photoreceptor drum 5 after the development process reaches the position opposite the transfer device 9 (transfer nip). At the position of the transfer device 9, the toner image formed on the photoreceptor drum 5 is transferred onto the sheet P (this is the transfer process). A transfer bias with a polarity different from that of the toner is applied to the transfer device 9 (transfer roller). Then, the surface of the photoreceptor drum 5 after the transfer process reaches a position opposite the cleaning device 8. The cleaning device 8 then removes and recovers any untransferred toner remaining on the photoreceptor drum 5 (this is the cleaning process). Subsequently, the surface of the photoreceptor drum 5 passes through the static elimination section, and the series of imaging processes in the photoreceptor drum 5 is completed.

[0014] Meanwhile, the sheet P, which is transported to the position of the transfer device 9 (transfer nip), operates as follows: First, the uppermost sheet P stored in the paper feed unit 12 is fed by the paper feed roller towards a transport path where multiple transport roller pairs are installed. Then, the sheet P reaches the position of the timing roller 45. Once the sheet P reaches the position of the timing roller 45, it is transported towards the transfer device 9 (transfer nip) in order to align with the image formed on the photoreceptor drum 5.

[0015] After that, the sheet P after the transfer process passes through the position of the transfer device 9 and then reaches the fixing device 20 through the conveyance path. The sheet P that has reached the fixing device 20 (the sheet P carrying the unfixed image) is fed between the fixing roller 21 (which has a heater as a heating means installed inside) and the pressure roller 22, and the toner image (image) is fixed by the heat received from the fixing roller 21 and the pressure received from both members 21 and 22. The sheet P on which the toner image has been fixed is discharged from the image forming apparatus main body 1 after being sent out from between the fixing roller 21 and the pressure roller 22 (the fixing nip). In this way, a series of image forming processes is completed.

[0016] Hereinafter, the fixing device 20 installed in the image forming apparatus 1 will be described in more detail. As shown in FIG. 2, the fixing device 20 includes a fixing roller 21 as a fixing rotating body, a heater 25 (fixing heater) as a heating means for heating the fixing device 20 (fixing roller 21), a pressure roller 22 as a pressure rotating body, a fixing temperature sensor 40 (fixing temperature detecting means), and the like.

[0017] The fixing roller 21 is a roller member having a multilayer structure in which a coating layer 21b (formed by laminating an elastic layer and a release layer) is formed on a hollow core metal 21a made of a metal material such as stainless steel, and forms a nip portion (fixing nip) by being pressed against the pressure roller 22 as a pressure rotating body. The fixing roller 21 is rotationally driven in the clockwise direction in FIG. 2 by a drive motor (not shown). Inside the hollow fixing roller 21 (core metal 21a), a heater 25 as a heating means is installed non-rotationally. The heater 25 is a halogen heater formed in a rod shape, and both ends thereof are fixed to the side plates of the fixing device 20. Then, when the main switch of the image forming apparatus main body 1 is turned on (power on), power is supplied from the power supply 55 to the heater 25. Then, the fixing roller 21 is heated by the radiant heat from the heater 25 whose output is controlled by the control unit 50, and heat is applied to the toner image on the sheet P from the surface of the further heated fixing roller 21. The output control of the heater 25 is performed based on the detection result of the roller surface temperature (fixing temperature) by the non-contact type (or contact type) fixing temperature sensor 40 facing the surface of the fixing roller 21. Specifically, an AC voltage is applied from the power supply 55 to the heater 25 for only the energization time determined based on the detection result of the fixing temperature sensor 40. By such output control (on / off control) of the heater 25, the temperature of the fixing roller 21 (fixing temperature) can be adjusted and controlled to a desired temperature (target control temperature). Also, the pressure roller 22 as a pressure rotating body is a roller member having an elastic layer formed on a core metal. The pressure roller 22 rotates in a driven manner in the counterclockwise direction of FIG. 2 as the fixing roller 21 rotates.

[0018] Hereinafter, the characteristic configurations and operations of the image forming apparatus 1 in the present embodiment will be described. As described above using FIGS. 1 and 2, the image forming apparatus 1 in the present embodiment is provided with a fixing device 20 that heats the toner image onto the surface of the sheet P by a heater 25 (fixing heater) as a heating means. The heater 25 as a heating means is controlled to be on and off based on the fixing temperature (the temperature detected by the fixing temperature sensor 40) in the fixing device 20 in the continuous printing mode. Further, the image forming apparatus 1 is provided with an in-machine temperature sensor 80 as temperature detection means for detecting the temperature inside the image forming apparatus main body (in-machine temperature). The in-machine temperature sensor 80 is a temperature sensor that indirectly (or directly) detects the temperature of the image forming section 4 that forms a toner image on the surface of the photosensitive drum 5 (photosensitive member). Specifically, the in-machine temperature sensor 80 is installed near the developing device 7 (image forming section 4) and detects the surrounding temperature (atmospheric temperature). Then, the information on the detected temperature (in-machine temperature) detected by the in-machine temperature sensor 80 is sent to the control unit 50 (see FIG. 2). Thereby, the control unit 50 can grasp the change in the in-machine temperature.

[0019] In this embodiment, the image forming apparatus 1 is configured to perform a "continuous printing mode" that continuously performs printing operations (image forming processes) on multiple sheets P. Specifically, the "continuous printing mode" can take the following forms: (1) printing (copying) multiple copies of a single document D placed on the document tray of the document transport unit 10 (or on the contact glass of the document reading unit 2); or (2) printing (copying) multiple copies one-to-one of multiple documents D placed on the document tray of the document transport unit 10. This continuous printing mode is performed based on user operations and commands on the operation display panel 90. In any case, the desired number of sheets P are sequentially fed from the paper feed unit 12 at intervals (spaces between sheets), and the image forming process (printing) described earlier using Figure 1 is performed continuously in one job with synchronized timing. In continuous printing mode, the image forming apparatus 1 does not stop operating, and basically, except for the paper feed unit 12 (or document transport unit 10) intermittently feeding sheets P (or documents D), other drive members and electrical components operate continuously.

[0020] Referring to Figures 3 and 5, in this embodiment, when the temperature detected by the in-machine temperature sensor 80 (temperature detection means) reaches or exceeds the first execution temperature T1 (for example, about 49°C) during the execution of the "continuous printing mode," the system switches to an "intermittent printing mode" which alternates between printing a predetermined number of pages and stopping printing for a predetermined period of time. Then, when the temperature detected by the in-machine temperature sensor 80 (temperature detection means) falls below the first release temperature T3 (a temperature lower than the first execution temperature T1, for example, about 47°C), the "intermittent printing mode" is deactivated and the system switches back to the "continuous printing mode." In other words, in Figure 3, intermittent printing mode is performed when the internal temperature is within range A1. As described above, "intermittent printing mode" alternates between printing a predetermined number of pages (for example, 3 pages) and stopping printing for a predetermined time N (for example, 10 seconds). Unlike continuous printing mode, where multiple printing operations are performed in one job, intermittent printing mode divides the printing into multiple jobs. Therefore, when intermittent printing mode is executed, printing productivity decreases compared to continuous printing mode, but the rise in the machine's internal temperature is reduced (the internal temperature tends to decrease) because the printing operation is interrupted intermittently.

[0021] Referring to Figures 3 and 5, in this embodiment, the "intermittent printing mode" is set to stop heating the fuser device 20 (fusing roller 21) by the heater 25 (heating means) if the temperature detected by the in-machine temperature sensor 80 (temperature detection means) does not drop to the first release temperature T3 even after a predetermined time M1 has elapsed since the start of the intermittent printing mode. In intermittent printing mode, the fuser unit 20 is basically heated by the heater 25 (heating is controlled by on / off) just like in continuous printing mode. However, if the internal temperature does not decrease as intended even after switching to intermittent printing mode, it is assumed that there are other factors preventing the internal temperature from decreasing, and the intermittent printing mode is continued with the heater 25 turned off. In other words, there are two types of intermittent printing mode: a first intermittent printing mode with the heater 25 turned on, and a second intermittent printing mode with the heater 25 turned off. Specifically, referring to Figure 3, if the internal temperature in the intermittent printing mode follows the change (trajectory) shown by the dashed line, the heater 25 (power supply 55) will be turned off, assuming that the internal temperature does not fall to the first release temperature T3. When the heater 25 (power supply 55) is turned off in this intermittent printing mode, the target control temperature (fixing temperature setting) of the fixing temperature measured by the fixing temperature sensor 40 will decrease from that during continuous printing, as shown by the dashed line in Figure 4, and consequently the fixing temperature will decrease, as shown by the solid line in Figure 4.

[0022] This type of control is implemented because, even when switching to intermittent printing mode, if there are other factors besides continuous printing mode that prevent the internal temperature from decreasing as intended, the internal temperature may not decrease as planned. Other factors that hinder the reduction of the internal temperature include the temperature (room temperature) of the location where the image forming apparatus 1 is installed being too high, the exhaust port B of the image forming apparatus 1 (see Figure 1) being blocked (or nearly blocked) by the walls of the room, the exhaust fan 33 (see Figure 1) being faulty, and the exhaust filter 32 (see Figure 1) being clogged. Furthermore, if the temperature rise inside the image forming apparatus 1 cannot be sufficiently reduced even when the intermittent printing mode is executed, the toner may aggregate or melt in the image forming unit 4 due to the temperature rise, resulting in problems such as a decrease in the quality of the printed image or a malfunction of the image forming unit 4. In contrast, in this embodiment, the heater 25 (power supply 55) can be turned off in intermittent printing mode. Therefore, even if there are other factors that hinder the decrease in internal temperature as described above, it is possible to sufficiently reduce the temperature rise inside the image forming apparatus. In particular, in this embodiment, the printing mode is switched based on the internal temperature detected by the internal temperature sensor 80 installed near the image forming unit 4. This effectively reduces problems such as the toner condensing or melting in the image forming unit 4 due to the temperature rise, which degrades the quality of the printed image, and problems such as the image forming unit 4 malfunctioning. Furthermore, in intermittent printing mode, when the heater 25 (power supply 55) is turned off, in order to prevent a decrease in the fixation of the printed sheet P, the heater 25 can be turned off only when the printing operation is stopped in intermittent printing mode (only for a predetermined time N during which the printing operation is stopped).

[0023] As shown in Figures 3 and 5, in this embodiment, when the temperature detected by the in-machine temperature sensor 80 (temperature detection means) becomes 2.0 or higher than the 2.0 temperature T2 (which is higher than the 1.0 temperature T1) during intermittent printing mode, the machine switches to a "print stop mode" that stops the printing operation. Then, when the temperature detected by the in-machine temperature sensor 80 (temperature detection means) becomes 2.0 or lower than the 2.0 temperature T4 (which is higher than the 1.0 temperature T3 and lower than the 2.0 temperature T2), the print stop mode is deactivated and the machine switches back to intermittent printing mode. In other words, in Figure 3, the print stop mode is activated when the internal temperature of the machine is within the range A2. As mentioned above, "print stop mode" interrupts and stops the printing process. Therefore, when print stop mode is activated, printing productivity decreases compared to intermittent printing mode, but the rise in the machine's internal temperature is reduced (the internal temperature decreases) because the printing process is paused.

[0024] Referring to Figures 3 and 5, in this embodiment, the "print stop mode" is set to stop heating the fuser device 20 (fusing roller 21) by the heater 25 (heating means) if the temperature detected by the in-machine temperature sensor 80 (temperature detection means) does not drop to the second release temperature T4 even after a predetermined time M2 has elapsed since the start of the print stop mode. In print stop mode, the fuser unit 20 is basically heated by the heater 25 (heating is controlled by on / off) as in continuous print mode. However, if the internal temperature does not decrease as intended even after switching from intermittent print mode to print stop mode, it is assumed that there are other factors preventing the internal temperature from decreasing, and the print stop mode is continued with the heater 25 turned off. In other words, there are two print stop modes: a first print stop mode with the heater 25 turned on, and a second print stop mode with the heater 25 turned off. Specifically, referring to Figure 3, if the internal temperature of the machine follows the change (trajectory) shown by the dashed line when transitioning from the intermittent printing mode shown by the solid line to the print stop mode shown by the dashed line, the heater 25 (power supply 55) will be turned off, assuming that the internal temperature will not drop to the second release temperature T4. When the heater 25 (power supply 55) is turned off in the print stop mode in this way, the target control temperature (fixing temperature setting) of the fixing temperature measured by the fixing temperature sensor 40 will decrease from that during continuous printing, as shown by the dashed line in Figure 4, and consequently the fixing temperature will decrease, as shown by the solid line in Figure 4.

[0025] This type of control is implemented because even when switching from intermittent printing mode to print-stop mode, if there are other major factors preventing the internal temperature from decreasing as described earlier, the internal temperature will not decrease as intended. Furthermore, if the temperature rise inside the image forming apparatus 1 cannot be sufficiently reduced even when the print stop mode is executed, the toner may aggregate or melt in the image forming unit 4 due to the temperature rise, resulting in problems such as a decrease in the quality of the printed image or a malfunction of the image forming unit 4. In contrast, in this embodiment, the heater 25 (power supply 55) is configured to be turned off in print stop mode. Therefore, even if there are other factors that hinder the decrease in internal temperature as described above, it becomes possible to sufficiently reduce the temperature rise inside the image forming apparatus.

[0026] Figure 3 is a graph showing an example of how the print mode changes when continuous printing mode is started. In the example shown in Figure 3, continuous printing mode is started, the internal temperature reaches the first operating temperature T1, and the system switches to intermittent printing mode. Subsequently, the internal temperature drops to the first release temperature T3, and continuous printing mode is resumed. The internal temperature then reaches the first operating temperature T1 again, and the system switches to intermittent printing mode. However, before the predetermined time M1 has elapsed, the internal temperature rises to the second operating temperature T2, and the system switches to print stop mode. Subsequently, as shown by the solid line, the internal temperature drops to the second release temperature T4, and intermittent printing mode is resumed. Then, the internal temperature drops further to the first release temperature T3, and continuous printing mode is resumed.

[0027] In this embodiment, when switching from "intermittent printing mode" to "print stop mode," the system is controlled to display a message on the operation display panel 90, which acts as a display unit, to lower the internal temperature (internal temperature) of the image forming apparatus body 1. As explained earlier, when transitioning from intermittent printing mode to print-stop mode, there are significant factors other than the printing mode itself that prevent the internal temperature from decreasing. Therefore, a message will be displayed on the operation display panel 90 to address these factors and prompt the user to take action. Specific examples of messages include: "The room temperature may be too high, please check the room temperature," "Please check if the device's exhaust vent is blocked," "The exhaust fan may need maintenance, please contact a service technician," and "Please replace the exhaust filter." By displaying such information, it becomes possible to eliminate factors that hinder the reduction of cabin temperature. In this embodiment, even if the heater 25 is turned off while the intermittent printing mode is running, the same display as described above can be shown for the same reason.

[0028] In this embodiment, even if the temperature detected by the in-machine temperature sensor 80 (temperature detection means) rises to or above the second execution temperature T2 while the intermittent printing mode is being executed, the control can be changed to continue executing the intermittent printing mode without switching from the intermittent printing mode to the print stop mode. In this embodiment, as explained earlier, if the internal temperature does not drop to the first release temperature T3 even after a predetermined time M1 has elapsed since the start of the intermittent printing mode, the heater 25 is turned off. If the internal temperature rises to the second execution temperature T2 before the predetermined time M1 has elapsed since the start of the intermittent printing mode, the system switches to the print stop mode. When the heater 25 is turned off, as in the former case, the system returns to the continuous printing mode when the internal temperature drops to the first release temperature T3. When the system switches to the print stop mode, as in the latter case, the system returns to the intermittent printing mode when the internal temperature drops to the second release temperature T4, and finally returns to the continuous printing mode when the internal temperature drops to the first release temperature T3. However, depending on how the user uses the image forming apparatus 1, it is possible that controlling only the former case may result in a shorter overall return time to the continuous printing mode than controlling both cases together. Therefore, by configuring the system to allow the user to choose whether to control both the former and the latter together, or to control only the former, it is possible to provide the user with a highly productive device. Furthermore, based on the user's usage of the image forming apparatus 1, the system can use AI to predict the recovery time when both the former and the latter are controlled together, and the recovery time when only the former is controlled, and display the prediction results on the operation display panel 90. In this way, the user can select settings that suit their needs based on the prediction results.

[0029] Below, an example of the control flow at the start of the continuous printing mode in this embodiment will be described using Figure 5. As shown in Figure 5, first, when the user operates the operation display panel 90 to start the continuous printing mode (step S1), it is determined whether the desired number of sheets to be printed based on the user's operation / command has been completed (step S2), and the series of prints (jobs) is terminated when the desired number of sheets to be printed is confirmed (step S3). If the desired number of pages have not been printed, the machine temperature sensor 80 determines whether the internal temperature T is equal to or greater than the first execution temperature T1 (step S4). If the internal temperature T does not reach the first execution temperature T1, the continuous printing mode continues and the flow from step S2 onwards is repeated. In contrast, if the internal temperature T reaches the first execution temperature T1, the continuous printing mode is interrupted and the intermittent printing mode is started (step S5). Then, it is determined whether the internal temperature T is equal to or greater than the second execution temperature T2 (step S6). If the result is that the internal temperature T has not reached the second execution temperature T2, the intermittent printing mode continues and it is determined whether the internal temperature T has decreased to or below the first release temperature T3 (step S7). If the internal temperature T is below the first release temperature T3, it is determined that the internal temperature T has decreased sufficiently and no problems will occur due to temperature rise, and the system returns to continuous printing mode and the flow from step S2 onwards is repeated. Note that the determination in step S6 is performed from the start of the intermittent printing mode in step S5 until a predetermined time M1 has elapsed. In contrast, if the internal temperature T in step S7 is not below the first release temperature T3, it is determined in step S5 whether a predetermined time M1 has elapsed since the start of the intermittent printing mode (step S8). If the predetermined time M1 has elapsed, the heater 25 (fuser heater) is turned off (step S9). Then, while continuing the intermittent printing mode with the heater 25 turned off, it is determined whether the internal temperature T has dropped to below the first release temperature T3 (step S10). Once it is confirmed that the internal temperature T has dropped to below the first release temperature T3, it is determined that the internal temperature T has dropped sufficiently and that no problems will occur due to temperature rise, and the system returns to continuous printing mode and the flow from step S2 onwards is repeated.

[0030] In contrast, if the internal temperature T reaches the second operating temperature T2 in step S6, the intermittent printing mode is interrupted and the printing stop mode is started (step S11). At this time, a message to lower the internal temperature is displayed on the operation display panel 90. Then, while the print stop mode continues, it is determined whether the internal temperature T has dropped to below the second release temperature T4 (step S12). If the internal temperature T falls below the second release temperature T4, it is determined that the internal temperature T has dropped smoothly and that no problems will occur even if a certain amount of printing is performed, and the system returns to intermittent printing mode and the flow from step S6 onwards is repeated. In contrast, if the internal temperature T in step S12 is not below the second release temperature T4, it is determined in step S13 whether a predetermined time M2 has elapsed since the start of the print stop mode in step S11. If the predetermined time M2 has elapsed, the heater 25 (fuser heater) is turned off (step S14). Then, with the heater 25 turned off, the print stop mode continues, and it is determined whether the internal temperature T has dropped to below the second release temperature T4 (step S15). Once it is confirmed that the internal temperature T is below the second release temperature T4, it is determined that the internal temperature T has dropped smoothly and that no problems will occur even if a certain amount of printing is performed, and the system returns to intermittent printing mode and the flow from step S6 onwards is repeated.

[0031] <Variation> Referring to Figures 6 and 7, in the modified image forming apparatus 1, if heating of the fixing device 20 by the heater 25 (heating means) is stopped in "print stop mode", the heating of the fixing device 20 by the heater 25 is stopped from the time the next "intermittent printing mode" or "print stop mode" is executed. In other words, in a single continuous printing mode, when the printer first switches to print stop mode, it switches between a first print stop mode with the heater 25 turned on and a second print stop mode with the heater 25 turned off, depending on the decrease in the internal temperature of the machine. However, if the second print stop mode (heater off) is executed during the first print stop mode, even if the printer subsequently returns to intermittent printing mode or the print stop mode is executed again, those modes will be executed with the heater 25 turned off. This type of control is implemented because, if the second print stop mode is executed during the first print stop mode, it is highly likely that there is a major factor preventing the reduction of the internal temperature as described earlier. Therefore, it is more efficient to turn off the heater 25 from the beginning during the subsequent intermittent print mode or print stop mode to reduce the internal temperature.

[0032] In another modified example, if heating of the fuser 20 by the heater 25 (heating means) is stopped in "print stop mode," the system is controlled so that at least one of the second execution temperature T2 and the second release temperature T4 is changed when "intermittent printing mode" or "print stop mode" is executed next. In other words, if, during a single continuous printing cycle, the printer first transitions to print stop mode and executes the second print stop mode (heater off), then even if it subsequently returns to intermittent printing mode or executes print stop mode again, the second execution temperature T2 and the second release temperature T4 will be changed in those modes. Specifically, in the modified example, the second execution temperature T2 and the second release temperature T4 are each reduced by about 2°C from their initial set temperatures. The reason for implementing this type of control is that if the second print stop mode is executed during the first print stop mode, it is highly likely that there is a major factor preventing the reduction of the internal temperature as described earlier. Therefore, by optimizing (changing) the second execution temperature T2 and the second release temperature T4 in the subsequent intermittent print mode or print stop mode, it is possible to quickly determine whether or not the factor preventing the reduction of the internal temperature has been eliminated.

[0033] The control flow at the start of continuous printing mode in a modified example will be explained below using Figures 6 and 7. As shown in Figure 6, when the continuous printing mode is started by the user operating the operation display panel 90 (step S1), steps S2 to S15 are performed as in Figure 5 described earlier. However, between step S5 and step S6, it is determined whether the heater 25 (fuser heater) was turned off in the previous print stop mode (step S19). If it is determined that the heater 25 was not turned off in the previous print stop mode, the flow from step S6 onwards is repeated. In response to this, if it is determined in step S19 that the heater 25 was turned off in the previous print stop mode, the control flow shown in Figure 7 is executed. As shown in Figure 7, first, the initially set second execution temperature T2 and second release temperature T4 are changed to the second execution temperature T2' and second release temperature T4' (step S20). Then, the heater 25 (fuser heater) is turned off (step S21). Then, it is determined whether the internal temperature T has become equal to or greater than the second release temperature T2' (step S22). As a result, if the internal temperature T is not above the second release temperature T2', the intermittent printing mode is continued with the heater 25 turned off, and it is determined whether the internal temperature T has dropped to or below the first release temperature T3 (step S22). If the internal temperature T is found to be below the first release temperature T3, it is determined that the internal temperature T has dropped sufficiently, and the system returns to continuous printing mode (heater 25 is turned on), and the flow from step S2 onwards is repeated. In contrast, if the internal temperature T is above the second execution temperature T2' in step S22, the intermittent printing mode is interrupted and the print stop mode is started (step S25). Then, while the print stop mode continues, it is determined whether the internal temperature T has dropped to below the second release temperature T4' (step S26). If the internal temperature T is below the second release temperature T4', it is assumed that the internal temperature T is decreasing smoothly, and the system returns to the intermittent printing mode (heater 25 remains off) and the flow from step S23 onwards is repeated.

[0034] As described above, the image forming apparatus 1 in this embodiment is equipped with a fixing device 20 that is heated by a heater 25 (heating means) to fix a toner image to the surface of a sheet P, and an internal temperature sensor 80 (temperature detection means) that detects the internal temperature of the image forming apparatus body 1. When the temperature detected by the internal temperature sensor 80 rises to or above the first execution temperature T1 during continuous printing mode, the system switches to intermittent printing mode, which alternates between printing a predetermined number of sheets and stopping printing for a predetermined period of time. When the temperature detected by the internal temperature sensor 80 falls to or below the first release temperature T3, which is lower than the first execution temperature T1, the intermittent printing mode is deactivated and the system switches back to continuous printing mode. Furthermore, in intermittent printing mode, if the temperature detected by the internal temperature sensor 80 does not fall to the first release temperature T3 even after a predetermined time M1 has elapsed since the start of intermittent printing mode, the heating of the fixing device 20 by the heater 25 is stopped. This makes it possible to sufficiently reduce the temperature rise inside the image forming apparatus 1.

[0035] In this embodiment, the present invention was applied to a monochrome image forming apparatus 1, but it can naturally also be applied to a color image forming apparatus. Furthermore, in this embodiment, the present invention was applied to an image forming apparatus 1 equipped with a thermal heater type fixing device 20 using a heater 25 as a heating means. However, the application of the present invention is not limited to this, and for example, the present invention can also be applied to an image forming apparatus equipped with an electromagnetic induction type (IH type) fixing device using an electromagnetic induction coil as a heating means, or an image forming apparatus equipped with a resistance heating type fixing device using a resistance heating element as a heating means. And even in those cases, the same effects as those of this embodiment can be obtained.

[0036] It is clear that the present invention is not limited to this embodiment, and that this embodiment can be modified as appropriate within the scope of the technical concept of the present invention, in addition to what is suggested here. Furthermore, the number, position, shape, etc. of the constituent members are not limited to this embodiment, and can be set to a number, position, shape, etc. that is suitable for carrying out the present invention. [Explanation of Symbols]

[0037] 1. Image forming apparatus (image forming apparatus main unit), 4 Imaging section, 20 Fixing device, 25 Heater (fixing heater, heating means), 31 Exhaust duct, 32 Exhaust filters, 33 Exhaust fan, 40 Fixing temperature sensor (fixing temperature detection means), 80 In-flight temperature sensor (temperature sensor, temperature detection means), 90 Operation display panel (display unit), P sheet (paper).

[0038] Furthermore, the embodiments of the present invention can also be, for example, combinations of appendices 1 to 8 as follows. (Note 1) A fixing device that heats the sheet using a heating means to fix a toner image onto the surface, A temperature detection means for detecting the internal temperature of the image forming apparatus body, Equipped with, During continuous printing mode, which performs printing operations on multiple sheets in succession, when the temperature detected by the temperature detection means reaches or exceeds the first execution temperature, the system switches to intermittent printing mode, which alternately repeats printing operations for a predetermined number of sheets and a predetermined period of time during printing operations. When the temperature detected by the temperature detection means falls below the first execution temperature, which is the first release temperature, the intermittent printing mode is deactivated and the system switches back to continuous printing mode. The image forming apparatus is characterized in that the intermittent printing mode stops heating the fixing device by the heating means if the temperature detected by the temperature detection means does not drop to the first release temperature even after a predetermined time has elapsed since the start of the intermittent printing mode. (Note 2) The image forming apparatus according to Appendix 1, characterized in that, during the execution of the intermittent printing mode, when the temperature detected by the temperature detection means becomes a second execution temperature or higher, which is higher than the first execution temperature, the system switches to a print stop mode that stops the printing operation, and when the temperature detected by the temperature detection means becomes a second release temperature or lower, which is higher than the first release temperature and lower than the second execution temperature, the print stop mode is deactivated and the system switches back to the intermittent printing mode. (Note 3) The image forming apparatus according to Appendix 2, characterized in that when the system switches from the intermittent printing mode to the print stop mode, a message for reducing the internal temperature of the image forming apparatus is displayed on the display unit. (Note 4) The image forming apparatus according to Appendix 2 or Appendix 3, characterized in that, during the execution of the intermittent printing mode, even if the temperature detected by the temperature detection means becomes equal to or greater than the second execution temperature, the control can be changed to continue executing the intermittent printing mode without switching from the intermittent printing mode to the printing stop mode. (Note 5) The image forming apparatus according to any one of the appendices 2 to 4, characterized in that the printing stop mode stops heating the fixing device by the heating means when the temperature detected by the temperature detection means does not drop to the second release temperature even after a predetermined time has elapsed since the printing stop mode was started. (Note 6) The image forming apparatus according to Appendix 5, characterized in that, if heating of the fixing device by the heating means is stopped in the printing stop mode, when the intermittent printing mode or the printing stop mode is executed next, heating of the fixing device by the heating means is stopped from the time the execution starts. (Note 7) The image forming apparatus according to Appendix 5 or Appendix 6, characterized in that when heating of the fixing device by the heating means is stopped in the printing stop mode, at least one of the second execution temperature and the second release temperature is changed when the intermittent printing mode or the printing stop mode is executed next. (Note 8) The heating means is a heater that is controlled on and off based on the fixing temperature in the fixing device in the continuous printing mode, The image forming apparatus according to any one of the appendices 1 to 7, characterized in that the temperature detection means is a temperature sensor that detects the temperature of the imaging unit that forms a toner image on the surface of the photoreceptor. [Prior art documents] [Patent Documents]

[0039] [Patent Document 1] Japanese Patent Publication No. 2012-198495

Claims

1. A fixing device that heats the sheet using a heating means to fix a toner image onto the surface, A temperature detection means for detecting the internal temperature of the image forming apparatus body, Equipped with, During continuous printing mode, in which printing operations are performed on multiple sheets in succession, when the temperature detected by the temperature detection means reaches or exceeds the first execution temperature, the system switches to intermittent printing mode, which alternately repeats printing operations for a predetermined number of sheets and stopping printing operations for a predetermined period of time. When the temperature detected by the temperature detection means falls below the first release temperature, which is lower than the first execution temperature, the intermittent printing mode is deactivated and the system switches back to continuous printing mode. The intermittent printing mode is characterized in that, if the temperature detected by the temperature detection means does not drop to the first release temperature even after a predetermined time has elapsed since the start of the intermittent printing mode, the heating means stops heating the fixing device.

2. The image forming apparatus according to claim 1, characterized in that, during the execution of the intermittent printing mode, when the temperature detected by the temperature detection means becomes a second execution temperature or higher, which is higher than the first execution temperature, the system switches to a print stop mode that stops the printing operation, and when the temperature detected by the temperature detection means becomes a second release temperature or lower, which is higher than the first release temperature and lower than the second execution temperature, the print stop mode is deactivated and the system switches back to the intermittent printing mode.

3. The image forming apparatus according to claim 2, characterized in that when the system switches from the intermittent printing mode to the print stop mode, a message for reducing the internal temperature of the image forming apparatus is displayed on the display unit.

4. The image forming apparatus according to claim 2, characterized in that, during the execution of the intermittent printing mode, even if the temperature detected by the temperature detection means becomes equal to or greater than the second execution temperature, the control can be changed to continue executing the intermittent printing mode without switching from the intermittent printing mode to the printing stop mode.

5. The image forming apparatus according to claim 2, characterized in that the printing stop mode stops heating the fixing device by the heating means when the temperature detected by the temperature detection means does not fall to the second release temperature even after a predetermined time has elapsed since the printing stop mode was started.

6. The image forming apparatus according to claim 5, characterized in that, if heating of the fixing device by the heating means is stopped in the printing stop mode, when the intermittent printing mode or the printing stop mode is executed next, heating of the fixing device by the heating means is stopped from the time the execution starts.

7. The image forming apparatus according to claim 5 or 6, characterized in that when heating of the fixing device by the heating means is stopped in the printing stop mode, at least one of the second execution temperature and the second release temperature is changed when the intermittent printing mode or the printing stop mode is executed next.

8. The heating means is a heater that is controlled to be turned on and off based on the fixing temperature in the fixing device in the continuous printing mode, The image forming apparatus according to claim 1 or 2, characterized in that the temperature detection means is a temperature sensor that detects the temperature of the imaging unit that forms a toner image on the surface of the photoreceptor.

Images