Image forming apparatus and its control method

Abstract

This prevents printing from stopping and reduces the decrease in print throughput. [Solution] During image formation, the control unit stops the operation of the process unit and stops printing if the control temperature, determined based on the temperature acquired by the first temperature sensor, exceeds the first temperature. The control unit switches to standby insertion mode when it meets standby conditions, including the control temperature exceeding a second temperature lower than the first temperature. When printing in standby insertion mode, the control unit waits for a predetermined waiting time without operating the process unit after completing printing using the received print data (t8~t10). Then, if the control unit receives print data during the predetermined waiting time, it operates the process unit and performs printing after the predetermined waiting time has elapsed (t10).

Description

[Technical Field]

[0001] This disclosure relates to an image forming apparatus and a control method thereof. [Background technology]

[0002] An invention is known that controls the operation of an image forming apparatus to prevent the temperature from becoming too high. In the invention described in Patent Document 1, if the internal temperature of the machine exceeds a first threshold during image forming, the machine switches to low-speed printing. Furthermore, if the internal temperature exceeds a second threshold, which is higher than the first threshold, printing is stopped. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-184010 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, even when switching to slow printing, heat generation continues as long as the image formation process is ongoing. If slow printing continues, the printer may reach the temperature required to stop printing, causing it to halt. When printing slows down or stops, users perceive the printing process as slow. Furthermore, when printing stops, the throughput (pages printed per unit time) decreases, especially when multiple print jobs are received.

[0005] Therefore, this disclosure aims to suppress the cessation of printing and thereby suppress the decrease in printing throughput. [Means for solving the problem]

[0006] In view of the above-mentioned background, the image forming apparatus disclosed herein comprises a main housing, a process unit, a fuser, a first temperature sensor, and a control unit. The process unit has a photosensitive drum and forms a toner image on the sheet. The fixing device includes a heater, and fixes a toner image on a sheet by heat. A first temperature sensor acquires a temperature inside a main body housing. When fixing a toner image on a sheet, a control section controls the heater such that the temperature of the fixing device reaches a fixing temperature. During image formation, when a control temperature determined based on the temperature acquired by the first temperature sensor exceeds a first temperature, the control section stops the operation of a process unit and stops printing. When a standby condition including that the control temperature exceeds a second temperature lower than the first temperature is satisfied, the control section shifts to a standby insertion mode. When performing printing in the standby insertion mode, after completing printing based on received print data and before executing printing based on next print data, the control section inserts a predetermined standby time, and waits without operating the process unit during the predetermined standby time. Then, when the control section receives print data during waiting for the predetermined standby time, after the predetermined standby time elapses, the control section operates the process unit to execute printing.

[0007] When entering the standby insertion mode, after completing printing based on received print data, the control section waits without operating the process unit for the predetermined standby time. Even when the control section receives print data during waiting for the predetermined standby time, after the predetermined standby time elapses, the control section operates the process unit to execute printing. Accordingly, since the next printing is started after the temperature decreases, stopping of the printing operation can be suppressed, and a decrease in printing throughput can be suppressed.

[0008] The standby condition may include that, in a state where the control temperature exceeds the second temperature, completion of printing by received print data has been performed a predetermined number of times.

[0009] Even after the control temperature exceeds the second temperature, by starting the predetermined number of times of printing without waiting, a decrease in printing throughput can be suppressed.

[0010] The control section may stop power supply to the heater during the predetermined standby time.

[0011] By stopping the power supply to the heater for a predetermined waiting period, the temperature inside the main unit's casing can be reduced.

[0012] After determining that the standby conditions have been met, the control unit may terminate the standby insertion mode if the control temperature falls below the third temperature, which is lower than or equal to the second temperature. If the control unit terminates the standby insertion mode, it will complete printing using the received print data and then control the heater to maintain the fuser at a standby temperature lower than the fuser temperature.

[0013] By maintaining the fuser at standby temperature while waiting for print data, printing can begin quickly when the next print data is received.

[0014] The control unit may perform cleaning of the photosensitive drum after completing printing using the received print data. When printing in standby insertion mode, the control unit performs cleaning after completing printing using the received print data. After that, the control unit waits for a predetermined waiting time without operating the process unit. If the control unit receives print data while performing cleaning or while waiting for the predetermined waiting time, it operates the process unit and performs printing after the predetermined waiting time has elapsed.

[0015] The image forming apparatus may further include a display panel. The control unit may display the remaining waiting time on the display panel in standby insertion mode.

[0016] When the waiting time is displayed on the display panel, the user can wait with peace of mind for the printing process to begin.

[0017] In standby insertion mode, the control unit may set a predetermined waiting time to a longer value if the number of printable pages included in the print data is large.

[0018] When printing a large number of pages consecutively, the temperature inside the image forming apparatus tends to rise. The more pages included in the print data, the longer the waiting time before printing starts can suppress the temperature rise of the image forming apparatus after printing begins.

[0019] The control unit may determine the control temperature based on the temperature acquired by the first temperature sensor and the operating amount of the process unit.

[0020] The image forming apparatus may further include a second temperature sensor for acquiring the temperature outside the main housing. The control unit may determine the control temperature based on the temperature acquired by the first temperature sensor, the operating amount of the process unit, and the temperature acquired by the second temperature sensor.

[0021] This disclosure provides a control method for an image forming apparatus comprising a main housing, a process unit, a fuser, a first temperature sensor, and a control unit. The process unit forms a toner image on a sheet. The fuser has a heater and fixes the toner image on the sheet by heat. The first temperature sensor acquires the temperature inside the main housing.

[0022] When fixing the toner image on the sheet, the control unit controls the heater so that the fuser temperature reaches the fixing temperature. During image formation, if the control temperature, determined based on the temperature acquired by the first temperature sensor, exceeds the first temperature, the control unit stops the operation of the process unit and stops printing. The control unit switches to standby insertion mode when it meets standby conditions, including the control temperature exceeding a second temperature lower than the first temperature. When printing in standby insertion mode, the control unit waits for a predetermined waiting time without operating the process unit after completing printing with the received print data. Then, if the control unit receives print data during the predetermined waiting time, it operates the process unit and performs printing after the predetermined waiting time has elapsed. [Effects of the Invention]

[0023] According to this disclosure, it is possible to suppress printing stoppages and thus suppress a decrease in printing throughput. [Brief explanation of the drawing]

[0024] [Figure 1] This is a diagram showing the configuration of an image forming apparatus. [Figure 2] This diagram illustrates the separation and contact states between the photosensitive drum and the developing roller. [Figure 3] This is a thermal circuit showing the heat entering and leaving the layer thickness regulating blade. [Figure 4] This is a flowchart showing the processing performed by the control unit. [Figure 5] This is a flowchart showing the cooldown process. [Figure 6] This is a timing chart illustrating the standby insertion mode. [Figure 7] This graph shows an example of how the control temperature changes. [Modes for carrying out the invention]

[0025] Next, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. As shown in Figure 1, the image forming apparatus 1 comprises a main body housing 10, a paper feeding unit 20, an image forming unit 30, a transport unit 90, and a control unit 100. The image forming apparatus 1 is a color printer capable of forming multi-colored images.

[0026] The main housing 10 has a first opening 10A, a front cover 11, a second opening 10B, and a rear cover 12. The first opening 10A is an opening through which the process unit U, described later, can pass. The front cover 11 is rotatable between an open position that opens the first opening 10A and a closed position that closes the first opening 10A.

[0027] The second opening 10B is an opening through which the seat S can pass. The rear cover 12 is rotatable between an open position that opens the second opening 10B and a closed position that closes the second opening 10B.

[0028] The paper feeding unit 20 supplies sheets S to the image forming unit 30. The paper feeding unit 20 comprises a paper feeding tray 21 and a sheet transport mechanism 22. The paper feeding tray 21 holds the sheets S. The sheet transport mechanism 22 transports the sheets S from the paper feeding tray 21 to the image forming unit 30.

[0029] The image forming unit 30 forms an image on the fed sheet S. The image forming unit 30 comprises a scanner unit 40, a process unit U, a transfer unit 70, a belt cleaner 78, and a fuser 80.

[0030] The scanner unit 40 includes a laser light-emitting unit (not shown), a polygon mirror, a lens, and a reflector. The scanner unit 40 irradiates the surface of each photosensitive drum 61 with a laser beam.

[0031] The process unit U has a photosensitive drum 61. The process unit U forms a toner image on the sheet S. The process unit U is retractable from the main housing 10 through a first opening 10A. The process unit U includes four cartridges 50 and a drawer 60.

[0032] The cartridge 50 is removable from the drawer 60. The cartridge 50 comprises a housing 51, a developing roller 52, and a layer thickness regulating blade 53. The housing 51 of the four cartridges 50 contains toners of yellow, magenta, cyan, and black. The layer thickness regulating blade 53 contacts the developing roller 52 to regulate the thickness of the toner layer on the developing roller 52.

[0033] Cartridge 50 contains yellow, magenta, cyan, or black toner. To identify the toner color, the symbols Y, M, C, and K are assigned to each cartridge, corresponding to yellow, magenta, cyan, and black. Cartridges 50Y, 50M, 50C, and 50K are arranged in this order from upstream to downstream in the transport direction of sheet S.

[0034] With the process unit U mounted in the image forming position of the main housing 10, cartridge 50Y is closest to the first aperture 10A, and cartridge 50K is furthest from the first aperture 10A. Cartridge 50K is closer to the fuser 80 than cartridge 50Y.

[0035] The drawer 60 can be pulled out in the pulling direction D from the image forming position of the main housing 10. Here, the image forming position refers to the position of the drawer 60 when image forming is performed. The pulling direction D is a direction that intersects the vertical direction. In this embodiment, the pulling direction D is the horizontal direction. The drawer 60 comprises a photosensitive drum 61, a charger (not shown), a frame 62, a first temperature sensor SE1, and a first contact CN1. The frame 62 detachably holds four cartridges 50. Four photosensitive drums 61 and chargers are provided on the frame 62, corresponding to the four developing rollers 52.

[0036] Frame 62 is supported on the main housing 10 so as to be movable in the pulling direction D. The first temperature sensor SE1 is, for example, a thermistor. The first temperature sensor SE1 obtains the internal temperature, which is the temperature inside the main housing 10. The first contact CN1 is electrically connected to the first temperature sensor SE1 via wiring.

[0037] The first temperature sensor SE1 and the first contact CN1 are located upstream of the outermost cartridge 50K in the drawer 60's withdrawal direction D. In other words, the first temperature sensor SE1 and the first contact CN1 are located between the outermost cartridge 50K and the fuser 80 in the drawer 60's withdrawal direction D. The distance from the first temperature sensor SE1 to cartridge 50K is smaller than the distance from the first temperature sensor SE1 to cartridge 50Y.

[0038] The main housing 10 is equipped with a second contact CN2 that is electrically connected to the control unit 100 via wiring. The first contact CN1 is connected to the second contact CN2 when the drawer 60 is positioned in the image forming position of the main housing 10. Specifically, when the drawer 60 is positioned in the image forming position, the first contact CN1 is connected to the second contact CN2.

[0039] Furthermore, when the drawer 60 is pulled out from the main housing 10, the first contact CN1 is separated from the second contact CN2. More specifically, when the drawer 60 is removed from the image forming position, the first contact CN1 is separated from the second contact CN2.

[0040] The transfer unit 70 comprises a drive roller 71, a driven roller 72, a conveyor belt 73, a transfer roller 74, and a backup roller 75. The conveyor belt 73 is an endless belt. The drive roller 71 and the driven roller 72 are rollers that rotate the conveyor belt 73. The transfer rollers 74 are rollers that clamp the conveyor belt 73 between themselves and the corresponding photosensitive drum 61, and four of them are arranged facing each photosensitive drum 61.

[0041] The backup roller 75 contacts the inner surface of the conveyor belt 73 and sandwiches the conveyor belt 73 between itself and the belt cleaning roller 78A of the belt cleaner 78, which will be described later.

[0042] The belt cleaner 78 comprises a belt cleaning roller 78A, a recovery roller 78B, a scraping blade 78C, and a storage section 78D. The belt cleaner 78 is configured to recover toner from the conveyor belt 73 into the storage section 78D.

[0043] More specifically, the belt cleaning roller 78A contacts the outer surface of the conveyor belt 73 and collects the toner adhering to the outer surface of the conveyor belt 73. The recovery roller 78B contacts the belt cleaning roller 78A and collects the toner on the belt cleaning roller 78A. The scraping blade 78C contacts the recovery roller 78B and scrapes off the toner on the recovery roller 78B. The storage unit 78D collects the toner scraped off the recovery roller 78B by the scraping blade 78C.

[0044] The fuser unit 80 is a device that fixes the toner image on the sheet S by heat. The fuser unit 80 includes a heating roller 81 that is heated by a heater H and a pressure roller 82 that is pressed against the heating roller 81.

[0045] In the image forming unit 30, the surface of each photosensitive drum 61 is uniformly charged by a charger and then exposed by the scanner unit 40. This forms an electrostatic latent image based on the image data on each photosensitive drum 61. Subsequently, the developing roller 52 supplies toner from the storage unit 51 onto the electrostatic latent image on the photosensitive drum 61, thereby forming a toner image on the photosensitive drum 61.

[0046] Next, the sheet S supplied onto the conveyor belt 73 passes between each photosensitive drum 61 and each transfer roller 74. At this time, the toner image formed on each photosensitive drum 61 is transferred onto the sheet S. Then, as the sheet S passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the sheet S is heat-fixed.

[0047] The transport unit 90 discharges the sheet S, which has been unloaded from the image forming unit 30, into the discharge tray 13 of the main housing 10. The transport unit 90 also reverses the front and back of the sheet S, on which an image has been formed by the image forming unit 30, and transports the sheet S back to the image forming unit 30. Specifically, the transport unit 90 mainly comprises a transport path 91, a discharge roller 92, and a re-transport path 93.

[0048] The transport path 91 is a path that guides the sheet S from the fuser 80 to the discharge tray 13.

[0049] The discharge roller 92 is configured to rotate in both forward and reverse directions. When rotating forward, the discharge roller 92 discharges the sheet S that has been removed from the image forming unit 30 to the discharge tray 13, and when rotating reverse, it transports the sheet S into the main body housing 10.

[0050] The re-transport path 93 is configured to guide the sheet S, on which an image has been formed on one side by the image forming unit 30, back to the image forming unit 30 by passing it under the paper feeding unit 20.

[0051] In the transport unit 90, once image formation is complete, the sheet S discharged from the image forming unit 30 is transported along the transport path 91 by the forward-rotating discharge roller 92. The sheet S is then discharged outside the main housing 10 and placed on the discharge tray 13. If an image is to be formed on the other side of a sheet S that already has an image formed on one side, the discharge roller 92 reverses direction before the entire sheet S is completely discharged outside the main housing 10. This pulls the sheet S back into the main housing 10, and it is transported from the transport path 91 to the re-transport path 93. The sheet S is then transported along the re-transport path 93 and transported back to the image forming unit 30 by the paper feeding unit 20.

[0052] The main unit enclosure 10 includes a fan 14, an air intake 15, a display panel 16, and a second temperature sensor SE2.

[0053] Fan 14 is a fan that cools the inside of the main unit housing 10 and is positioned above the fuser unit 80. Fan 14 is positioned between the fuser unit 80 and the drawer 60. Fan 14 is configured to draw in air from inside the main unit housing 10 and expel it to the outside.

[0054] The air intake 15 is an opening for drawing air into the main body housing 10 from the outside. The air intake 15 is located on the opposite side of the process unit U from the fan 14. The air intake 15 is located below the process unit U. In other words, the air intake 15 is located in a position that is less affected by the heat generated by the cartridge 50. This allows the fan 14 to be activated to guide air from outside the main body housing 10 into the process unit U, thereby lowering the temperature of the process unit U.

[0055] The display panel 16 is a panel that presents information to the user using text and graphics. The display panel 16 may be, for example, an LCD panel or an LED display.

[0056] The second temperature sensor SE2 is, for example, a thermistor and is positioned facing the inside of the air intake port 15. The second temperature sensor SE2 detects the temperature of the air taken in from the air intake port 15. Thus, the second temperature sensor SE2 is configured to acquire the ambient temperature, which is the temperature outside the main housing 10. The second temperature sensor SE2 is connected to the control unit 100 via wiring.

[0057] The control unit 100 includes a CPU, ROM, RAM, etc., and is configured to perform various processes in response to the reception of a print command, etc., according to a pre-prepared program. As shown in Figure 2, the control unit 100 can execute color mode, monochrome mode, and full separation mode. The control unit 100 switches between each mode by controlling the separation mechanism 200, which causes the developing roller 52 to come into contact with or separate from the photosensitive drum 61.

[0058] The color mode is an operating mode for forming a multi-color image. In color mode, the control unit 100 brings all the developing rollers 52Y, 52M, 52C, and 52K into contact with the corresponding photosensitive drums 61Y, 61M, 61C, and 61K. The control unit 100 then rotates all the developing rollers 52 and all the photosensitive drums 61. In other words, when forming a multi-color image, the control unit 100 operates all the cartridges 50.

[0059] Monochrome mode is the operating mode for forming a single-color image. In monochrome mode, the control unit 100 makes only the black developing roller 52K contact the photosensitive drum 61K. The control unit 100 separates the other three color developing rollers 52Y, 52M, and 52C from their corresponding photosensitive drums 61Y, 61M, and 61C. In addition, in monochrome mode, the control unit 100 rotates only the developing roller 52K and all the photosensitive drums 61. On the other hand, the control unit 100 stops the other developing rollers 52Y, 52M, and 52C. In other words, when forming a single-color image, the control unit 100 operates only cartridge 50K, without operating the color cartridges 50Y, 50M, and 50C.

[0060] The full separation mode is an operating mode in which all developing rollers 52Y, 52M, 52C, and 52K are separated from their corresponding photosensitive drums 61Y, 61M, 61C, and 61K. The control unit 100 executes the full separation mode, for example, when cleaning the photosensitive drum 61.

[0061] The control unit 100 controls the printing operation and fan operation so that the temperature of the process unit U is within an appropriate range, based on the control temperature T. The control temperature T is the temperature estimated to be the temperature of the cartridge 50. In this embodiment, the temperature T of the layer thickness regulating blade 53 is... B It is estimated to be so.

[0062] The control unit 100 determines the control temperature T based on the temperature acquired by the first temperature sensor SE1, the operating amount of the process unit U, and the temperature acquired by the second temperature sensor SE2. The control unit 100 is configured to calculate a first control temperature corresponding to cartridge 50K and a second control temperature corresponding to cartridge 50Y. The control unit 100 then sets the higher of the first and second control temperatures as the control temperature T.

[0063] Specifically, the control unit 100 calculates the differential temperature at predetermined time intervals based on the internal machine temperature, the outside air temperature, the driving state of the developing roller 52, and the like. The differential temperature is the temperature change of the layer thickness regulating blade 53 from the previous calculation to the current time. The control unit 100 takes the sum of the obtained differential temperature and the previously calculated temperature of the layer thickness regulating blade 53 as the current temperature of the layer thickness regulating blade 53.

[0064] The current temperature T of the layer thickness regulating blade 53 B (n)[°C] is obtained by the following formula (1). In formula (1), T B (n-1)[°C] is the previously calculated temperature of the layer thickness regulating blade 53. ΔT B [°C] is the differential temperature of the layer thickness regulating blade 53. T B (n)=T B (n-1)+ΔT B ··(1)

[0065] ΔT in formula (1) B [°C] is obtained by the following formula (2) using heat quantity ΔE in-B (n)[J], heat quantity ΔE out-B (n)[J], and heat generation amount Q B [W] as shown in FIG. 3. In formula (2), ΔE in-B (n)[J] is the amount of heat transferred from the periphery of the first temperature sensor SE1 to the layer thickness regulating blade 53. ΔE out-B (n)[J] is the amount of heat transferred from the layer thickness regulating blade 53 to the outside air. Q B [W] is the amount of heat generated by the layer thickness regulating blade 53. C B [J / °C] is the heat capacity of the layer thickness regulating blade 53. Δt[s] is the time elapsed from the previous calculation to the current time. ΔT B =(ΔE in-B (n)-ΔE out-B (n)+Q B ×Δt) / C B ··(2)

[0066] (2) ΔE in-B (n)[J] can be found by the following equation (3). In equation (3), T in (n-1)[°C] is the cabin temperature obtained last time. T B (n-1)[°C] is the temperature of the layer thickness regulating blade 53 calculated in the previous calculation. R in-B [°C / W] represents the thermal resistance between the cabin air and the layer thickness regulating blade 53. ΔE in-B (n) = (T in (n-1)-T B (n-1) × Δt / R in-B (3)

[0067] (2) ΔE out-B (n)[J] can be found by the following equation (4). In equation (4), T out (n-1)[°C] is the ambient temperature obtained last time. R out-B [°C / W] represents the thermal resistance between the ambient temperature and the layer thickness regulating blade 53. ΔE out-B (n) = (T B (n-1)-T out (n-1) × Δt / R out-B (4)

[0068] R in equations (3) and (4) in-B , R out-B The first control temperature and the second control temperature are set to different values. In other words, the first function used to calculate the first control temperature and the second function used to calculate the second control temperature are R in-B , R out-B They are different.

[0069] The amount of heat generated by the layer thickness regulating blade 53 in equation (2) Q B This parameter changes according to the operating amount of the process unit U and corresponds to the operating amount of the cartridge 50. Heat generation QB This can be set, for example, based on the driving time, stopping time, and rotational speed of the developing roller 52.

[0070] From equations (2) to (4), the control unit 100 determines the temperature T of the layer thickness regulating blade 53K, which is the first control temperature. B The control unit 100 calculates the temperature T of the layer thickness regulating blade 53Y, which is the second control temperature. B Perform the calculation.

[0071] The control unit 100 receives the above-mentioned constants (Q) from the storage unit. B , C B , R in-B , R out-B The system obtains the following constants and uses them to calculate the temperature of the layer thickness regulating blade 53. Each constant is a value corresponding to the drive state of the developing roller 52, the open / closed state of the rear cover 12, whether the printing is single-sided or double-sided, the size of the sheet S, the drive state of the fan 14, and the state of the fuser 80.

[0072] Next, the printing process by the control unit 100 will be described in detail. When fixing the toner image on the sheet S, the control unit 100 controls the heater H so that the temperature of the fuser 80 becomes the fixing temperature. During image formation, if the control temperature T, which is determined based on the temperature acquired by the first temperature sensor SE1, exceeds the first temperature T1, the control unit 100 performs a cool-down process. In the cool-down process, the control unit 100 stops the operation of the process unit U and stops printing. In the cool-down process, the control unit 100 stops the power supply to the heater H while keeping the fan 14 running.

[0073] The control unit 100 switches to standby insertion mode when it meets standby conditions, including the control temperature T exceeding a second temperature T2 which is lower than the first temperature T1. When printing in standby insertion mode, the control unit 100 completes printing using the received print data and then waits for a predetermined waiting time without operating the process unit U. During the waiting time, the control unit 100 keeps the fan 14 running but stops powering the heater H. In standby insertion mode, the control unit 100 displays the remaining waiting time on the display panel 16. The predetermined waiting time is not particularly limited, but for example, it is 5 seconds.

[0074] Then, if the control unit 100 receives print data while waiting for a predetermined waiting period, it operates the process unit U to execute printing after the predetermined waiting period has elapsed.

[0075] In this embodiment, the standby condition is defined as the control temperature T exceeding the second temperature T2, and the completion of printing using received print data a predetermined number of times. In other words, the control unit 100 does not determine that the standby condition has been met simply because the control temperature T has exceeded the second temperature T2 once.

[0076] After determining that the standby conditions have been met, the control unit 100 may terminate the standby insertion mode if the control temperature T falls below the third temperature, which is less than or equal to the second temperature T2. In this embodiment, the third temperature is the same as the second temperature T2. However, the third temperature may be lower than the second temperature. When the control unit 100 terminates the standby insertion mode, it completes printing using the received print data and then controls the heater H to maintain the fuser 80 at a standby temperature lower than the fixing temperature. As a result, the image forming apparatus 1 enters a ready mode, waiting for print data with the fuser 80 at the standby temperature.

[0077] After completing printing using the received print data, the control unit 100 performs cleaning of the photosensitive drum 61. When performing cleaning, the control unit 100 ejects toner from a drum cleaner (not shown) onto the photosensitive drum 61. The control unit 100 then moves the toner from the photosensitive drum 61 onto the surface of the transport belt 73, and cleans the transport belt 73 with a belt cleaner 78.

[0078] Furthermore, when printing in standby insertion mode, the control unit 100 completes printing using the received print data and then performs cleaning. After that, the control unit 100 waits for a predetermined waiting time without operating the process unit U.

[0079] Even if the control unit 100 receives print data while cleaning is being performed, it will operate the process unit U to execute printing after a predetermined waiting period has elapsed.

[0080] In standby insertion mode, the control unit 100 sets a predetermined standby time to a longer value as the number of printable pages included in the print data increases. However, the standby time may be a constant time regardless of conditions such as the control temperature T and the number of printable pages.

[0081] An example of the processing performed by the control unit 100 to achieve the above-described control will be explained with reference to Figures 4 and 5. The control unit 100 repeatedly executes the processing shown in Figure 4.

[0082] As shown in Figure 4, the control unit 100 determines whether or not it has received print data (S100). If the control unit 100 has not received print data (No), it waits until it receives print data.

[0083] When the control unit 100 receives print data (S100, Yes), it determines whether the ready state time RT, which is the time the unit has been waiting in a ready state, is less than the threshold RTth (S110). If the control unit 100 determines that the ready state time RT is not less than the threshold RTth (No), it sets the count value N to 0 (S111). The count value N is the number of times printing has been completed using the received print data while the control temperature T is above the second temperature T2. If the ready state time RT is not less than the threshold RTth, the temperature of the process unit U decreases, so the count value N is reset to 0. After setting the count value N to 0, the control unit 100 sets the standby flag FW to 0 (S112) and starts printing (S120). The standby flag FW is a flag indicating whether or not the unit is in standby insertion mode. If the ready state time RT is not less than the threshold RTth, the temperature of the process unit U decreases, so the standby flag FW is set to 0 and the standby insertion mode is terminated.

[0084] If the control unit 100 determines in step S110 that the ready state time RT is less than the threshold RTth (Yes), it determines whether the control temperature T is greater than the second temperature T2 (S113). If the control unit 100 determines that the control temperature T is less than or equal to the second temperature T2 (No), it sets the standby flag FW to 0 (S112) and starts printing (S120). In this case, since the temperature of the process unit U has decreased, the standby insertion mode is terminated. In this embodiment, the third temperature is T2, so determining No in step S113 means that the control temperature T is less than or equal to the third temperature.

[0085] In step S113, the control unit 100 determines that the control temperature T is greater than the second temperature T2 (Yes), and increments the count value N (S114). Then, it determines whether the count value N is greater than a predetermined number of times Nth (S115). The predetermined number of times Nth is not particularly limited, but one example is 4. If the control unit 100 determines that the count value N is greater than the predetermined number of times Nth, it sets the standby flag FW to 1 (S116). After that, the control unit 100 sets a waiting time according to the number of prints included in the received data (S117) and starts printing (S120). In step S115, if the control unit 100 determines that the count value N is not greater than the predetermined number of times Nth, it sets the standby flag FW to 0 (S112) and starts printing (S120).

[0086] After starting printing in step S120, the control unit 100 determines at an appropriate time whether the control temperature T has become greater than the first temperature T1 (S121). If the control unit 100 determines that the control temperature T is greater than the first temperature T1 (Yes), it executes a cool-down process (S180). If the control unit 100 determines that the control temperature T is less than or equal to the first temperature T1 (No), it does not execute a cool-down process (S180).

[0087] As shown in Figure 5, the control unit 100 stops printing (S181) during the cool-down process (S180). Stopping printing includes stopping the operation of the process unit U, stopping exposure, and stopping the power supply to the heater H. When printing stops, the control unit 100 activates the fan 14. Then, the control unit 100 sets the standby flag FW to 0 and the count value N to 0 (S182). Next, the control unit 100 determines whether the control temperature T has fallen below the recovery temperature TR (S183). If the control unit 100 determines that the control temperature T has fallen below the recovery temperature TR (No), it waits until the control temperature T falls below the recovery temperature TR. If the control unit 100 determines that the control temperature T has fallen below the recovery temperature TR (S183, Yes), it resumes printing (S184) and terminates the cool-down process. The recovery temperature TR is, for example, a temperature lower than the first temperature T1 and higher than the second temperature T2.

[0088] Returning to Figure 4, the control unit 100 determines whether printing of the received print data is complete after the cool-down process or after determining No in step S121 (S125). If the control unit 100 determines that printing is not complete (No), it returns to step S121 and continues the printing process. If the control unit 100 determines that printing is complete (S125, Yes), it performs a cleaning process (S126).

[0089] After the cleaning process, the control unit 100 determines whether the standby flag FW is 1 or not (S130). If the control unit 100 determines that the standby flag FW is 1 (Yes), it waits for a predetermined waiting time to elapse (S131, No). If the control unit 100 determines in step S130 that the standby flag FW is not 1 (No), or after the predetermined waiting time has elapsed in step S131 (Yes), it determines whether there is print data (S132). If the control unit 100 determines that there is print data (Yes), it returns to step S110 and executes the processing for when print data is received. If the control unit 100 determines that there is no print data (S132, No), it returns to step S100 and waits for print data.

[0090] An example of the operation of the image forming apparatus 1 based on the above processing will now be explained. Figure 6 is a timing chart of the printing operation after the control temperature T exceeds the second temperature T2. When print data is input, the count value N increases and becomes 4 at time t1. After the printing of the received print data is completed (t2), the control unit 100 performs a cleaning process (t3~t4). During the cleaning process, the standby flag FW is still 0, so without waiting for a predetermined waiting time, the control unit 100 maintains the fuser 80 at the standby temperature and puts it into ready mode (t4~t5).

[0091] When the control unit 100 receives print data at time t5 in ready mode, it starts printing. The count value N increases as print data is input. When the count value N reaches 5 at time t5, the control unit 100 sets the standby flag FW to 1. As a result, the image forming apparatus 1 enters standby insertion mode. After printing of the received print data is completed (t6), the control unit 100 performs a cleaning process (t7-t8). Then, the control unit 100 stops the process unit U and heater H and waits for a predetermined waiting time (t8-t10).

[0092] When the control unit 100 receives the next print data during a predetermined waiting period (t8 to t10) (t9), it does not immediately start printing, but starts the printing process after the predetermined waiting period has ended (t10).

[0093] When a large number of print data are input intermittently, the control temperature T changes as shown in Figure 7. The numbers accompanying the graph in Figure 7 represent the count value N. The count value N is counted from the point when the control temperature T exceeds the second temperature T2. When the count value N reaches 5, the standby flag FW becomes 1, and the system enters standby insertion mode. Then, after each print completion, the control unit 100 performs a cleaning process and waits for a predetermined waiting time. As a result, in standby insertion mode, the temperature rise gradient is gentler compared to before. Therefore, the time when the control temperature T reaches the first temperature T1 is delayed, and the user is not kept waiting for a long time. In addition, although a 5-second wait occurs after each print completion in standby insertion mode, the system does not easily enter the cooling-down process. Therefore, the overall print throughput is improved in the long term.

[0094] The image forming apparatus 1 of this embodiment, as described above, can achieve the following effects. When the control unit 100 enters standby insertion mode, it completes printing using the received print data and then waits for a predetermined waiting time without operating the process unit U. In other words, in standby insertion mode, the next print job is started only after the temperature has dropped, thus preventing the printing operation from stopping. This helps to suppress a decrease in printing throughput.

[0095] Even after the control temperature T exceeds the second temperature T2, a predetermined number of prints can be started without waiting, thereby suppressing a decrease in print throughput.

[0096] The control unit 100 can lower the temperature inside the main body housing 10 by stopping the power supply to the heater H for a predetermined waiting period.

[0097] The control unit 100 maintains the fuser 80 at a standby temperature while waiting for print data. Therefore, when the control unit 100 receives the next print data, it can quickly start the printing operation.

[0098] In standby insertion mode, the waiting time is displayed on the display panel 16. This allows the user to wait for the printing operation to start with peace of mind.

[0099] When printing a large number of pages consecutively, the temperature inside the image forming apparatus 1 tends to rise. However, the image forming apparatus 1 increases the waiting time before printing starts as the number of pages in the print data increases. Therefore, the image forming apparatus 1 can suppress the temperature rise after printing starts.

[0100] Although one embodiment of the present disclosure has been described above, the mode of implementation can be modified as appropriate. For example, the control temperature T may be calculated using the measurement value of the first temperature sensor SE1, rather than using the measurement value of the second temperature sensor SE2. Alternatively, the control temperature T may be the value measured by the first temperature sensor SE1 itself.

[0101] In this embodiment, the control unit 100 started the standby insertion mode after the control temperature T exceeded the second temperature T2 and after completing a predetermined number of prints. However, the standby insertion mode may be started immediately after the control temperature T exceeds the second temperature T2.

[0102] An intake fan is provided inside the intake port 15, and the control unit 100 may operate the intake fan during the cool-down process and standby time.

[0103] In the embodiment, the control unit 100 performed cleaning of the photosensitive drum 61 each time it completed printing using the received print data. However, cleaning of the photosensitive drum 61 is not necessary.

[0104] Displaying the waiting time on the display panel 16 is not necessary.

[0105] Furthermore, the elements described in the above-mentioned embodiments and modifications may be combined in any way. [Explanation of Symbols]

[0106] 1. Image forming apparatus 10 Main Unit 30 Image forming unit 50 cartridges 80 Fuser 100 Control Unit H heater SE1 First Temperature Sensor U Process Unit

Claims

1. The main casing and A process unit having a photosensitive drum and forming a toner image on a sheet, A fuser unit having a heater that fixes the toner image on the sheet by heat, A first temperature sensor that acquires the temperature inside the main body housing, It comprises a control unit and, The control unit, When fixing the toner image on the sheet, the heater is controlled so that the temperature of the fuser reaches the fixing temperature. During image formation, if the control temperature determined based on the temperature acquired by the first temperature sensor exceeds the first temperature, the process unit stops operating and printing is stopped. When the standby conditions are met, including the control temperature exceeding a second temperature lower than the first temperature, the system transitions to standby insertion mode. In the standby insertion mode, when printing is performed, the process unit is kept idle for a predetermined waiting period after completing printing using the received print data, and if print data is received during the predetermined waiting period, the process unit is activated after the predetermined waiting period has elapsed to perform printing.

2. The image forming apparatus according to claim 1, characterized in that the standby condition includes the completion of printing using received print data a predetermined number of times while the control temperature exceeds the second temperature.

3. The control unit, The image forming apparatus according to claim 1, characterized in that power to the heater is stopped during the predetermined waiting time.

4. The control unit, The image forming apparatus according to claim 1, characterized in that, after determining that the standby conditions are met, if the control temperature falls below the third temperature which is lower than or equal to the second temperature, the standby insertion mode is terminated, printing using the received print data is completed, and then the heater is controlled to maintain the fuser at a standby temperature lower than the fixing temperature.

5. The control unit, After completing printing using the received print data, the photosensitive drum is cleaned. The image forming apparatus according to claim 1, characterized in that when printing in the standby insertion mode, after completing printing with the received print data, the cleaning is performed, and then the process unit is left idle for a predetermined waiting time, and if print data is received while the cleaning is being performed or while waiting for the predetermined waiting time, the process unit is operated and printing is performed after the predetermined waiting time has elapsed.

6. It also features a display panel, The control unit, The image forming apparatus according to claim 1, characterized in that the remaining waiting time is displayed on the display panel in the standby insertion mode.

7. The control unit, The image forming apparatus according to claim 1, characterized in that, in the standby insertion mode, the predetermined standby time is set to a longer value as the number of printable pages included in the print data increases.

8. The control unit, The image forming apparatus according to claim 1, characterized in that the control temperature is determined based on the temperature acquired by the first temperature sensor and the amount of operation of the process unit.

9. The system further includes a second temperature sensor for acquiring the temperature outside the main body housing, The control unit, The image forming apparatus according to claim 1, characterized in that the control temperature is determined based on the temperature acquired by the first temperature sensor, the amount of operation of the process unit, and the temperature acquired by the second temperature sensor.

10. The main casing and A process unit that forms a toner image on a sheet, A fuser unit having a heater that fixes the toner image on the sheet by heat, A first temperature sensor that acquires the temperature inside the main body housing, A control method for an image forming apparatus comprising a control unit, The control unit, When fixing the toner image on the sheet, the heater is controlled so that the temperature of the fuser reaches the fixing temperature. During image formation, if the control temperature determined based on the temperature acquired by the first temperature sensor exceeds the first temperature, the process unit stops operating and printing is stopped. When the standby conditions are met, including the control temperature exceeding a second temperature lower than the first temperature, the system transitions to standby insertion mode. A control method for an image forming apparatus, characterized in that, when printing in the standby insertion mode, after completing printing with received print data, the process unit is kept idle for a predetermined waiting time, and if print data is received during the predetermined waiting time, the process unit is operated after the predetermined waiting time has elapsed to perform printing.

Images