Image forming apparatus

Abstract

To provide an image forming apparatus that can prevent an increase in temperature of a process unit.SOLUTION: An image forming apparatus 1 comprises: a housing 10 that has an opening (rear opening 10B); a cover (rear cover 12) that opens and closes the opening, and in an open state, can eject a sheet S on which an image is formed from the opening; a process unit 31 that transfers toner images to the sheet S; a fixing unit 80 that has a heating unit 81 for heating the sheet S, fixes the toner images transferred by the process unit 31 to the sheet S, and is arranged between the cover in a closed state and the process unit 31; a fan 13 that, when driven, exhausts air inside the housing 10; and a control unit 100 that can execute a printing operation to form the image on the sheet S. When executing the printing operation, the control unit 100 drives the fan 13 at a first speed when the cover is closed, and drives the fan 13 at a second speed slower than the first speed when the cover is open.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image forming apparatus including a cover for opening and closing an opening of a housing.

Background Art

[0002] Conventionally, an image forming apparatus including a cover for opening and closing an opening of a housing has been known (Patent Document 1). In this technology, the image forming apparatus includes a fan for exhausting air inside the housing to the outside, and when the detected temperature of a thermistor for detecting the temperature of a fixing unit is higher than a threshold value, the control unit drives the fan at a high speed after the start of a printing operation, and when the detected temperature is lower than the threshold value, the control unit drives the fan at a low speed slower than the high speed for a predetermined time after the start of the printing operation, and drives the fan at a high speed after the elapse of the predetermined time. Further, when the cover (rear cover) is open, the control unit always drives the fan at a high speed during the printing operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the fan is driven at a high speed with the cover open, the flow rate of air flowing into the housing from the opening increases. In this case, if the air flowing into the housing from the opening passes near the fixing unit and is heated, and then flows into the process unit that transfers the toner image to the sheet, the process unit may become hot.

[0005] Therefore, an object of the present invention is to provide an image forming apparatus capable of suppressing a temperature rise of a process unit.

Means for Solving the Problems

[0006] The image forming apparatus for achieving the above-described object includes a housing having an opening, a cover for opening and closing the opening, the cover allowing a sheet on which an image has been formed in an open state to be discharged from the opening, a process unit for transferring a toner image onto the sheet, and a heating unit for heating the sheet, and a fixing unit for fixing the toner image transferred by the process unit onto the sheet, the fixing unit being disposed between the closed cover and the process unit, a fan for discharging air inside the housing when driven, and a control unit capable of executing a printing operation for forming an image on the sheet. When executing the printing operation, the control unit drives the fan at a first speed when the cover is closed, and drives the fan at a second speed slower than the first speed when the cover is open.

[0007] According to such a configuration, when executing the printing operation, when the cover is closed, by driving the fan at a high speed, the fixing unit and the process unit can be cooled by the airflow formed inside the housing. Also, when executing the printing operation, when the cover is open, by driving the fan at a low speed, the flow rate of the air flowing into the housing from the opening can be reduced. Thereby, it is possible to suppress the air heated by passing near the fixing unit from flowing into the process unit, and thus it is possible to suppress the temperature rise of the process unit.

[0008] Further, the image forming apparatus includes a temperature sensor, and the control unit can be configured to drive the fan at the second speed when the first temperature based on the detection result of the temperature sensor is less than the first threshold even when the cover is closed when executing the printing operation.

[0009] According to this, during printing, even when the cover is closed, when the first temperature is low, by driving the fan at a low speed, while cooling the fixing unit and the process unit, it is possible to suppress the fan from operating more than necessary.

[0010] Also, the first temperature can be configured to be a temperature obtained by correcting the measured value of the temperature sensor.

[0011] According to this, compared with the case of controlling the fan using the measured value of the temperature sensor, the fan can be controlled with high accuracy.

[0012] Further, the image forming apparatus includes a temperature sensor, and the control unit can execute a cooling operation of prohibiting the execution of the printing operation and cooling the fixing unit based on the detection result of the temperature sensor. When executing the cooling operation, the fan can be configured to be driven at a first speed.

[0013] According to this, by driving the fan at a high speed when executing the cooling operation, the flow rate of the air flowing near the fixing unit can be ensured. Thereby, the fixing unit can be efficiently cooled.

[0014] Further, the temperature sensor includes a fixing temperature sensor that detects the temperature of the heating unit, and the control unit can be configured to execute the cooling operation when a second temperature based on the detection result of the fixing temperature sensor is equal to or higher than a second threshold value.

[0015] According to this, since the cooling operation can be executed when the temperature of the heating unit is high, it is possible to suppress the temperature of the fixing unit from becoming too high.

[0016] Further, the temperature sensor includes a fixing temperature sensor that detects the temperature of the heating unit, and the control unit can execute a first printing operation of conveying a sheet at a first conveyance speed and a second printing operation of conveying the sheet at a second conveyance speed slower than the first conveyance speed as the printing operation. When the second temperature based on the detection result of the fixing temperature sensor is equal to or higher than the second threshold value, the second printing operation can be executed.

[0017] According to this, when the temperature of the heating unit is high, the second printing operation in which the heat of the fixing unit easily moves to the sheet can be executed, so that it is possible to suppress the temperature of the fixing unit from becoming too high.

[0018] Further, the temperature sensor includes an external temperature sensor that detects the temperature outside the housing, and the control unit may be configured to execute a cooling operation when a third temperature based on the detection result of the external temperature sensor is equal to or higher than a third threshold value.

[0019] According to this, a cooling operation can be executed when the temperature outside the housing is high.

[0020] Further, the temperature sensor includes an internal temperature sensor that detects the temperature inside the housing, and the control unit may be configured to execute a cooling operation when a fourth temperature based on the detection result of the internal temperature sensor is equal to or higher than a fourth threshold value.

[0021] According to this, a cooling operation can be executed when the temperature inside the housing is high.

[0022] Further, the temperature sensor includes an internal temperature sensor that detects the temperature inside the housing, and as a printing operation, the control unit can execute a first printing operation of conveying a sheet at a first conveyance speed and a second printing operation of conveying the sheet at a second conveyance speed slower than the first conveyance speed, and may be configured to execute the second printing operation when a fifth temperature based on the detection result of the internal temperature sensor is equal to or higher than a fifth threshold value.

[0023] According to this, when the temperature inside the housing is high and the temperature of the heating unit is likely to be high, a second printing operation in which the heat of the fixing unit easily moves to the sheet can be executed, so that it is possible to suppress the temperature of the fixing unit from becoming too high.

[0024] Further, the image forming apparatus includes an open / close detection sensor that detects the opening and closing of a cover, and the control unit may be configured to determine whether the cover is open or closed based on the detection result of the open / close detection sensor.

[0025] According to this, it is possible to determine whether the cover is open or closed according to the actual open / close state of the cover.

[0026] In addition, the image forming apparatus includes a temperature sensor, and in a standby state where the control unit waits for an input of a print job, when a first temperature based on a detection result of the temperature sensor is equal to or higher than a sixth threshold value, the fan is driven at a first speed, and when the first temperature is lower than the sixth threshold value and equal to or higher than a seventh threshold value lower than the sixth threshold value, the fan is driven at a second speed, and when the first temperature is lower than the seventh threshold value, the fan can be stopped.

[0027] According to this, during standby, when the first temperature is high, the fixing unit and the process unit can be cooled by driving the fan at a high speed. Also, when the first temperature is moderate, by driving the fan at a low speed, while cooling the fixing unit and the process unit, it is possible to suppress the fan from operating more than necessary. Further, when the first temperature is low, by stopping the fan, it is possible to suppress the fan from operating uselessly.

[0028] In addition, the control unit can be configured to drive the fan at a second speed even when the first temperature is equal to or higher than the sixth threshold value if the cover is open.

[0029] According to this, the flow rate of air flowing into the housing from the opening can be reduced, and thereby, it is possible to suppress the air heated by passing near the fixing unit from flowing into the process unit, so that the temperature rise of the process unit can be suppressed.

Advantages of the Invention

[0030] According to the present invention, the temperature rise of the process unit can be suppressed.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0032] Next, the first embodiment will be described. As shown in FIG. 1, the image forming apparatus 1 is a color printer, and includes a housing 10, a front cover 11, a rear cover 12 as an example of a cover, a sheet feeding unit 20, an image forming unit 30, a sheet conveying unit 90, and a control unit 100.

[0033] The housing 10 has a front opening 10A provided at the front and a rear opening 10B as an example of an opening provided at the rear. Further, the housing 10 has a discharge tray 10C provided at the upper part.

[0034] The front cover 11 is a cover that opens and closes the front opening 10A, and its lower end is rotatably supported by the housing 10. The front cover 11 is rotatable between a position where it closes the front opening 10A and a position where it opens the front opening 10A (not shown) with respect to the housing 10. The image forming apparatus 1 includes a first opening / closing sensor SC1 that detects the opening and closing of the front cover 11, and the control unit 100 determines whether the front cover 11 is open or closed based on the detection result of the first opening / closing sensor SC1.

[0035] The rear cover 12 is a cover that opens and closes the rear opening 10B, and its lower end is rotatably supported by the housing 10. The rear cover 12 is rotatable between a position where it closes the rear opening 10B and a position where it opens the rear opening 10B (see FIG. 7) with respect to the housing 10. The image forming apparatus 1 includes a second opening / closing sensor SC2 as an example of an opening / closing detection sensor that detects the opening and closing of the rear cover 12, and the control unit 100 determines whether the rear cover 12 is open or closed based on the detection result of the second opening / closing sensor SC2.

[0036] The sheet feeding unit 20 has a function of feeding the sheet S to the image forming unit 30, and includes a sheet tray 21 that houses the sheet S and a sheet feeding mechanism 22. The sheet tray 21 is detachable with respect to the housing 10 and is disposed at the lower part inside the housing 10 when mounted on the housing 10. The sheet feeding mechanism 22 separates the sheets S in the sheet tray 21 one by one and feeds them to the image forming unit 30.

[0037] The image forming unit 30 has a function of forming an image on the sheet S, and includes a process unit 31 that transfers a toner image to the sheet S and a fixing unit 80 that fixes the toner image transferred by the process unit 31 to the sheet S. The process unit 31 includes an exposure unit 40, a drum unit 50, four developing cartridges 60, and a transfer unit 70.

[0038] The exposure unit 40 is disposed at the upper part inside the housing 10 and includes a light source, a polygon mirror, a lens, a reflecting mirror, etc. (not shown). The exposure unit 40 exposes the surface of the photosensitive drum 51 by emitting a light beam indicated by a dashed line onto the surface of the photosensitive drum 51.

[0039] The drum unit 50 is disposed between the sheet tray 21 and the exposure unit 40 inside the housing 10, and includes four photosensitive drums 51, four chargers 52, and a support frame 55 that supports the photosensitive drums 51, etc. The drum unit 50 is detachable from the housing 10 through the front opening 10A with the front cover 11 open.

[0040] The developing cartridge 60 is detachably attached to the drum unit 50. Each developing cartridge 60 includes a developing roller 61, a supply roller 62, a layer thickness regulating blade 63, and a toner storage portion 64.

[0041] The transfer unit 70 is disposed between the sheet tray 21 and the drum unit 50 inside the housing 10, and includes a driving roller 71, a driven roller 72, a conveying belt 73, and four transfer rollers 74. The conveying belt 73 is stretched between the driving roller 71 and the driven roller 72, and the upper surface thereof is in contact with the photosensitive drum 51. The four transfer rollers 74 are disposed inside the conveying belt 73 so as to sandwich the conveying belt 73 between the corresponding photosensitive drums 51.

[0042] The fixing unit 80 is disposed behind the process unit 31 inside the housing 10. Further, the fixing unit 80 is disposed between the closed rear cover 12 and the process unit 31. The fixing unit 80 has a heating unit 81 that heats the sheet S, and a pressing unit 82 that sandwiches the sheet S between the heating unit 81. In the present embodiment, the heating unit 81 has a heating roller 81A and a heater 81B that heats the heating roller 81A. The pressing unit 82 has an endless belt (not shown by reference numerals), a pressing pad that sandwiches the endless belt between the heating unit 81, a holder that supports the pressing pad, a belt guide, etc.

[0043] The image forming unit 30 uniformly charges the surface of the photosensitive drum 51 by the charger 52, and exposes the surface of the photosensitive drum 51 by the exposure unit 40, thereby forming an electrostatic latent image on the surface of the photosensitive drum 51. Further, the image forming unit 30 supplies the toner in the toner storage unit 64 to the supply roller 62, and supplies it from the supply roller 62 to the developing roller 61. The toner supplied to the developing roller 61 enters between the developing roller 61 and the layer thickness regulating blade 63 as the developing roller 61 rotates, and is carried on the developing roller 61 as a thin layer with a constant thickness.

[0044] The image forming unit 30 supplies the toner carried on the developing roller 61 to the electrostatic latent image formed on the photosensitive drum 51, thereby forming a toner image on the surface of the photosensitive drum 51. Thereafter, the image forming unit 30 transfers the toner image on the photosensitive drum 51 to the sheet S by conveying the sheet S supplied from the sheet supply unit 20 between the photosensitive drum 51 and the conveyance belt 73. Thereafter, the image forming unit 30 fixes the toner image transferred to the sheet S to the sheet S by conveying the sheet S between the heating unit 81 and the pressure unit 82, thereby forming an image on the sheet S.

[0045] The sheet conveyance unit 90 has a function of conveying the sheet S conveyed from the image forming unit 30 outside the housing 10 or back to the image forming unit 30 again. The sheet conveyance unit 90 includes a first path 91, a second path 92, a third path 93, a first conveyance roller 94, a second conveyance roller 95, a first switchback roller 96, a second switchback roller 97, a plurality of third conveyance rollers 98, and a flapper 99. A part of the second path 92 is formed by the closed rear cover 12.

[0046] When the sheet conveyance unit 90 conveys the sheet S outside the housing 10 and the rear cover 12 is closed, the sheet S conveyed from the image forming unit 30 is conveyed by the first conveyance roller 94 and guided to the first path 91 by the flapper 99. Then, the sheet conveyance unit 90 conveys the sheet S guided to the first path 91 by the second conveyance roller 95 and the first switchback roller 96, and discharges it onto the discharge tray 10C.

[0047] Also, when the sheet conveyance unit 90 conveys the sheet S outside the housing 10 and the rear cover 12 is open, the sheet S conveyed from the image forming unit 30 is conveyed by the first conveyance roller 94 and guided rearward by the flapper 99 that has swung to the position indicated by the virtual line, and discharged onto the rear cover 12 in the open state through the rear opening 10B. The image forming apparatus 1 can form an image on the sheet S even when the rear cover 12 is open, and the rear cover 12 is a cover that can discharge the sheet S on which an image has been formed from the rear opening 10B in the open state.

[0048] Also, when the sheet conveyance unit 90 conveys the sheet S to the image forming unit 30 again, the sheet S conveyed from the image forming unit 30 is conveyed by the first conveyance roller 94 and guided to the first path 91 or the second path 92 by the flapper 99. When the sheet S is guided to the first path 91, the sheet conveyance unit 90 conveys the sheet S in the first path 91 to the third path 93 by the second conveyance roller 95 and the first switchback roller 96. Also, when the sheet S is guided to the second path 92, the sheet conveyance unit 90 conveys the sheet S in the second path 92 to the third path 93 by the second switchback roller 97.

[0049] The sheet S conveyed to the third path 93 is supplied to the image forming unit 30 again by the third conveyance roller 98 and the sheet supply mechanism 22. Then, after the image is formed on the sheet S by the image forming unit 30, the sheet S is discharged onto the discharge tray 10C by the sheet conveyance unit 90.

[0050] The image forming apparatus 1 further includes a fan 13, an internal temperature sensor ST1, a fixing temperature sensor ST2, an external temperature sensor ST3, and a patch reading sensor SP.

[0051] The fan 13 is provided to discharge the air inside the housing 10 to the outside of the housing 10 when driven. The housing 10 has a pair of left and right side frames (not shown), and the fan 13 is provided on the right side frame. The fan 13 is disposed between the process unit 31 and the rear cover 12 in a closed state when viewed from the left - right direction. Also, the fan 13 is disposed above the fixing unit 80 when viewed from the left - right direction. Note that a duct (not shown) extending left - right is provided between the process unit 31 and the rear cover 12 in a closed state and above the fixing unit 80, and the fan 13 is disposed on the right side of the duct. The fan 13 can be driven at a first speed and a second speed slower than the first speed. Hereinafter, the first speed is also referred to as "high speed", and the second speed is also referred to as "low speed".

[0052] The internal temperature sensor ST1 is a temperature sensor that detects the temperature inside the housing 10. The internal temperature sensor ST1 is disposed near the area between the drum unit 50 and the fixing unit 80 inside the housing 10. Specifically, the internal temperature sensor ST1 is disposed between the developing cartridge 60 (hereinafter referred to as "developing cartridge 60A") that is disposed most downstream in the conveyance direction of the sheet S and the fixing unit 80. The internal temperature sensor ST1 is provided at the rear part of the support frame 55. As the internal temperature sensor ST1, for example, a thermistor or the like can be used.

[0053] The fixing temperature sensor ST2 is a temperature sensor that detects the temperature of the fixing unit 80. Specifically, the fixing temperature sensor ST2 detects the temperature of the heating unit 81. The fixing temperature sensor ST2 is provided on the fixing unit 80 and is disposed to face the heating roller 81A in a non - contact state. As the fixing temperature sensor ST2, for example, a non - contact type thermistor or the like can be used.

[0054] The outside air temperature sensor ST3 is a temperature sensor that detects the temperature outside the housing 10. The housing 10 has an intake opening 10D provided at the lower part of the front end of the left side frame (not shown), and the outside air temperature sensor ST3 is provided to detect the temperature of the air taken in through the intake opening 10D. As the outside air temperature sensor ST3, for example, a thermistor or the like can be used.

[0055] The inside air temperature sensor ST1, the fixing temperature sensor ST2, and the outside air temperature sensor ST3 are examples of "temperature sensors". In other words, in the present embodiment, the "temperature sensor" includes the inside air temperature sensor ST1, the fixing temperature sensor ST2, and the outside air temperature sensor ST3.

[0056] The patch reading sensor SP is a sensor that detects a toner image (hereinafter referred to as "patch") transferred onto the conveyance belt 73. The patch reading sensor SP is arranged between the process unit 31 and the fixing unit 80 in the conveyance direction of the sheet S. Specifically, the patch reading sensor SP is arranged to face the rear part of the conveyance belt 73. As the patch reading sensor SP, for example, an optical reflection type sensor having a light emitting element and a light receiving element can be used. The image forming apparatus 1 executes position deviation correction, density correction, etc. by detecting the patch on the conveyance belt 73 with the patch reading sensor SP.

[0057] The control unit 100 includes a CPU, a RAM, a ROM, an input / output circuit, etc. The control unit 100 controls the sheet supply unit 20, the image forming unit 30, the sheet conveyance unit 90, and the fan 13 by performing various arithmetic processes based on programs, data, etc. stored in the ROM or the like.

[0058] The control unit 100 is capable of executing a printing operation for forming an image on the sheet S. When the control unit 100 receives a print job including a print start command, image data, etc., it executes the printing operation.

[0059] When the control unit 100 executes the printing operation, if the rear cover 12 is closed, the fan 13 is driven at high speed, and if the rear cover 12 is open, the fan 13 is driven at low speed. Further, in the present embodiment, when the control unit 100 executes the printing operation, even if the rear cover 12 is closed, if the corrected internal temperature T1 described later is less than the first threshold value Tth1, the fan 13 is driven at low speed.

[0060] That is, when the control unit 100 executes the printing operation, if the rear cover 12 is closed, the fan 13 is driven at high speed when the corrected internal temperature T1 is equal to or higher than the first threshold value Tth1, and the fan 13 is driven at low speed when the corrected internal temperature T1 is less than the first threshold value Tth1. Further, when the control unit 100 executes the printing operation, if the rear cover 12 is open, the fan 13 is driven at low speed regardless of the corrected internal temperature T1.

[0061] The corrected internal temperature T1 is an example of the first temperature based on the detection result of the temperature sensor, and in the present embodiment, it is the temperature obtained by correcting the measured value of the temperature sensor. Specifically, the corrected internal temperature T1 is the temperature obtained by correcting the measured value of the internal temperature sensor ST1.

[0062] The control unit 100 calculates the developing roller temperature T11, which is the temperature of the developing roller 61 of the developing cartridge 60A disposed closest to the fixing unit 80, as the corrected internal temperature T1, and the blade temperature T12, which is the temperature of the layer thickness regulating blade 63 of the developing cartridge 60A. The control unit 100 calculates the developing roller temperature T11 and the blade temperature T12 based on the internal temperature, which is the measured value of the internal temperature sensor ST1, the external temperature, which is the measured value of the external temperature sensor ST3, the driving state of the developing roller 61 of the developing cartridge 60A, and the like.

[0063] As an example, the control unit 100 calculates the developing roller temperature T11 by an arithmetic expression including terms containing the internal temperature of the machine and terms containing the external temperature of the machine. Further, the control unit 100 calculates the blade temperature T12 by an arithmetic expression including terms containing the internal temperature of the machine, terms containing the external temperature of the machine, and terms containing the calorific value (predetermined constant) of the layer thickness regulating blade 63 obtained from a ROM or the like according to the driving state of the developing roller 61 of the developing cartridge 60A.

[0064] The calculations of the developing roller temperature T11 and the blade temperature T12 can be performed, for example, by the method disclosed in Japanese Patent Application Laid-Open No. 2016-224374, so detailed description thereof is omitted in this specification.

[0065] When in the standby state waiting for the input of a printing job, the control unit 100 can execute a ready mode for maintaining the fixing unit 80 (heating unit 81) at a predetermined temperature and a sleep mode for turning off the heater 81B of the heating unit 81. During the execution of the ready mode, the temperature inside the housing 10 may rise.

[0066] Therefore, when in the standby state, if the corrected internal temperature T1 of the machine is equal to or higher than the sixth threshold value Tth12, the control unit 100 drives the fan 13 at high speed. Also, when in the standby state, if the corrected internal temperature T1 of the machine is less than the sixth threshold value Tth12 and equal to or higher than the seventh threshold value Tth11 which is lower than the sixth threshold value Tth12, the control unit 100 drives the fan 13 at low speed. Further, when in the standby state, if the corrected internal temperature T1 of the machine is less than the seventh threshold value Tth11, the control unit 100 stops the fan 13.

[0067] In addition, based on the detection results of the temperature sensors ST1 to ST3, the control unit 100 can further execute a cooling operation that prohibits the execution of the printing operation and cools the fixing unit 80. When executing the cooling operation, the control unit 100 prohibits the execution of the printing operation, turns off the heater 81B of the fixing unit 80, and drives the fan 13 at high speed. Furthermore, when executing the cooling operation, the control unit 100 drives the fan 13 at high speed regardless of whether the rear cover 12 is open or closed.

[0068] In addition, when the control unit 100 prohibits the execution of the printing operation along with the execution of the cooling operation, for example, when there is a sheet S before the supply starts, the supply of the sheet S to the image forming unit 30 is prohibited, and when there is a sheet S after the supply starts (the sheet S being conveyed), the sheet S is discharged outside the housing 10. The control unit 100 executes the cooling operation after interrupting the execution of the printing operation.

[0069] The control unit 100 executes the cooling operation when the outside temperature T3 is equal to or higher than the third threshold value Tth32. The outside temperature T3 is an example of a third temperature based on the detection result of the outside temperature sensor ST3, and in the present embodiment, it is the measured value of the outside temperature sensor ST3.

[0070] In addition, the control unit 100 executes the cooling operation when the corrected internal temperature T1 is equal to or higher than the fourth threshold value Tth43. In the present embodiment, the corrected internal temperature T1 is also an example of a fourth temperature based on the detection result of the internal temperature sensor ST1. In the present embodiment, the control unit 100 determines that the corrected internal temperature T1 is equal to or higher than the threshold value when at least one of the developing roller temperature T11 and the blade temperature T12 is equal to or higher than the threshold value, and determines that the corrected internal temperature T1 is lower than the threshold value (hereinafter) when both the developing roller temperature T11 and the blade temperature T12 are lower than the threshold value (hereinafter).

[0071] In addition, the control unit 100 executes the cooling operation when the fixing unit temperature T2 is equal to or higher than the second threshold value Tth22. The fixing unit temperature T2 is an example of a second temperature based on the detection result of the fixing temperature sensor ST2, and in the present embodiment, it is the measured value of the fixing temperature sensor ST2.

[0072] Next, the operation of the control unit 100 will be described with reference to the flowchart. When the control unit 100 is in a standby state waiting for the input of a print job, it repeatedly executes the fan control process during standby shown in FIG. 2.

[0073] As shown in FIG. 2, when in the standby state, the control unit 100 determines whether the corrected internal temperature T1 is equal to or higher than the seventh threshold value Tth11 (S11). When the corrected internal temperature T1 is less than the seventh threshold value Tth11 (S11, No), the control unit 100 stops the fan 13 (S12).

[0074] When the corrected internal temperature T1 is equal to or higher than the seventh threshold value Tth11 (S11, Yes), the control unit 100 determines whether the corrected internal temperature T1 is equal to or higher than the sixth threshold value Tth12, which is higher than the seventh threshold value Tth11 (S13). When the corrected internal temperature T1 is less than the sixth threshold value Tth12 (S13, No), the control unit 100 drives the fan 13 at a low speed (S15). When the corrected internal temperature T1 is equal to or higher than the sixth threshold value Tth12 (S13, Yes), the control unit 100 drives the fan 13 at a high speed (S16).

[0075] When the control unit 100 receives a print job, it executes the fan control process during printing shown in FIG. 3. As shown in FIG. 3, when the control unit 100 receives a print job, it determines whether the rear cover 12 is open or closed based on the detection result of the second open / close sensor SC2 (S21). When the rear cover 12 is open (S21, Yes), the control unit 100 drives the fan 13 at a low speed (S23).

[0076] When the rear cover 12 is closed (S21, No), the control unit 100 determines whether the corrected internal temperature T1 is less than the first threshold value Tth1 (S22). When the corrected internal temperature T1 is less than the first threshold value Tth1 (S22, Yes), the control unit 100 drives the fan 13 at a low speed (S23). When the corrected internal temperature T1 is equal to or higher than the first threshold value Tth1 (S22, No), the control unit 100 drives the fan 13 at a high speed (S24).

[0077] After driving the fan 13, the control unit 100 determines whether printing has ended (S25). If printing has not ended (S25, No), the control unit 100 returns to step S21 and executes the subsequent processing. If printing has ended (S25, Yes), the control unit 100 ends the fan control processing during printing.

[0078] Also, when receiving a print job, the control unit 100 executes the operation determination process shown in FIG. 4.

[0079] As shown in FIG. 4, when receiving a print job, the control unit 100 determines whether the outside temperature T3 is equal to or higher than the third threshold value Tth32 (S111). If the outside temperature T3 is less than the third threshold value Tth32 (S111, No), the control unit 100 determines whether the corrected internal temperature T1 is equal to or higher than the fourth threshold value Tth43 (S112). If the corrected internal temperature T1 is less than the fourth threshold value Tth43 (S112, No), the control unit 100 determines whether the fixing unit temperature T2 is equal to or higher than the second threshold value Tth22 (S113). If the fixing unit temperature T2 is less than the second threshold value Tth22 (S113, No), the control unit 100 executes a printing operation (S114).

[0080] If the outside temperature T3 is equal to or higher than the third threshold value Tth32 in step S111 (Yes), if the corrected internal temperature T1 is equal to or higher than the fourth threshold value Tth43 in step S112 (Yes), or if the fixing unit temperature T2 is equal to or higher than the second threshold value Tth22 in step S113 (Yes), the control unit 100 executes a cooling operation.

[0081] Specifically, as shown in FIG. 5, the control unit 100 first interrupts the printing operation (S131). For example, if there is a sheet S before the start of supply, the supply of the sheet S to the image forming unit 30 is prohibited. If there is a sheet S being conveyed, the sheet S is discharged outside the housing 10.

[0082] Thereafter, the control unit 100 turns off the heater 81B of the fixing unit 80 (S132). Also, regardless of whether the rear cover 12 is open or closed, the control unit 100 drives the fan 13 at high speed (S133). When performing the cooling operation, the control unit 100 temporarily ends the fan control process during printing shown in FIG. 3.

[0083] Thereafter, the control unit 100 determines whether the outside temperature T3 is equal to or lower than a threshold value Tth31 lower than the third threshold value Tth32 (S134). When the outside temperature T3 is higher than the threshold value Tth31 (S134), the control unit 100 returns to step S133 and executes the subsequent processing.

[0084] If in step S134 the outside temperature T3 is equal to or lower than the threshold value Tth31 (Yes), the control unit 100 determines whether the corrected internal temperature T1 is equal to or lower than a threshold value Tth42 lower than the fourth threshold value Tth43 (S135). When the corrected internal temperature T1 is higher than the threshold value Tth42 (S135, No), the control unit 100 returns to step S133 and executes the subsequent processing.

[0085] If in step S135 the corrected internal temperature T1 is equal to or lower than the threshold value Tth42 (Yes), the control unit 100 ends the cooling operation. Thereafter, as shown in FIG. 4, the control unit 100 resumes the printing operation (S114). When the cooling operation ends, the control unit 100 resumes the fan control process during printing shown in FIG. 3.

[0086] After starting or resuming the execution of the printing operation in step S114, the control unit 100 determines whether printing has ended (S115). If printing has not ended (S115, No), the control unit 100 returns to step S111 while continuing the execution of the printing operation and executes the subsequent processing. If printing has ended (S115, Yes), the control unit 100 ends the operation determination process.

[0087] According to the above first embodiment, when performing a printing operation, when the rear cover 12 is closed, the fan 13 is driven at a high speed, so that the fixing unit 80 and the process unit 31 can be cooled by the air flow formed in the housing 10. Further, when performing a printing operation, when the rear cover 12 is open, the fan 13 is driven at a slow speed, so that the temperature rise of the process unit 31 can be suppressed.

[0088] Specifically, as shown in FIG. 6, when performing a printing operation, when the rear cover 12 is closed, the fan 13 is driven at a high speed, so that the air in the housing 10 flows from the process unit 31 side toward the fan 13, and the air outside the housing 10 flows into the housing 10 from the first path 91 and the second path 92.

[0089] The air flowing from the process unit 31 side toward the fan 13 takes in the heat generated in the process unit 31 and is discharged from the fan 13 to the outside of the housing 10. Further, the air flowing into the housing 10 from the first path 91 and the second path 92 passes near the fixing unit 80, takes in the heat generated in the fixing unit 80, and is discharged from the fan 13 to the outside of the housing 10. Thereby, the fixing unit 80 and the process unit 31 can be cooled. Further, the air flowing into the housing 10 from the first path 91 and the second path 92 cools the sheet S (not shown) conveyed in the first path 91 and the second path 92.

[0090] As shown in FIG. 7(b) as a comparative example, when performing a printing operation, when the rear cover 12 is open and the fan 13 is driven at a high speed, the flow rate of the air flowing into the housing 10 from the rear opening 10B increases. In this case, when the air flowing into the housing 10 from the rear opening 10B passes near the fixing unit 80 and is heated, and then flows into the process unit 31 side, the process unit 31 (particularly near the developing cartridge 60A) and the vicinity of the patch reading sensor SP may become high temperature.

[0091] As shown in FIG. 7(a), in the present embodiment, when the printing operation is executed, if the rear cover 12 is open, the fan 13 is driven at a low speed to cool the fixing unit 80 while reducing the flow rate of the air flowing into the housing 10 from the rear opening 10B. Thereby, it is possible to suppress the heated air passing near the fixing unit 80 from flowing into the process unit 31 side, so that it is possible to suppress the temperature rise near the process unit 31 (near the developing cartridge 60A) and near the patch reading sensor SP.

[0092] Further, during printing, even when the rear cover 12 is closed, if the corrected internal temperature T1 of the machine is lower than the first threshold value Tth1, the fan 13 is driven at a slow speed to cool the fixing unit 80 and the process unit 31 while suppressing the fan 13 from operating more than necessary.

[0093] Also, since the corrected internal temperature T1 of the machine is the temperature obtained by correcting the measured value of the internal temperature sensor ST1 of the machine, the control of the fan 13 can be performed with higher accuracy as compared with the case where the fan 13 is controlled using the measured value of the internal temperature sensor ST1 of the machine.

[0094] Further, by driving the fan 13 at a high speed when the cooling operation is executed, the flow rate of the air flowing near the fixing unit 80 can be ensured. Thereby, the fixing unit 80 can be efficiently cooled.

[0095] Also, since the cooling operation is executed when the fixing unit temperature T2 is equal to or higher than the second threshold value Tth22, the cooling operation can be executed when the temperature of the heating unit 81 is high, and it is possible to suppress the temperature of the fixing unit 80 from becoming too high. Thereby, the fixing unit 80 can be used at a temperature below a predetermined temperature.

[0096] Also, since the cooling operation is executed when the external temperature T3 of the machine is equal to or higher than the third threshold value Tth32, the cooling operation can be executed when the temperature outside the housing 10 is high.

[0097] In addition, since the cooling operation is executed when the temperature T1 inside the correcting unit is equal to or higher than the fourth threshold value Tth43, the cooling operation can be executed when the temperature inside the housing 10 is high.

[0098] In addition, since it is determined whether the rear cover 12 is open or closed based on the detection result of the second opening / closing sensor SC2, it is possible to determine whether the rear cover 12 is open or closed according to the actual open / closed state of the rear cover 12.

[0099] In addition, during standby, when the temperature T1 inside the correcting unit is as high as the sixth threshold value Tth12 or higher, the fixing unit 80 and the process unit 31 can be cooled by driving the fan 13 at a high speed. Further, when the temperature T1 inside the correcting unit is moderate, that is, lower than the sixth threshold value Tth12 and equal to or higher than the seventh threshold value Tth11, the fixing unit 80 and the process unit 31 can be cooled by driving the fan 13 at a low speed, while suppressing the fan 13 from operating more than necessary. Further, when the temperature T1 inside the correcting unit is low, that is, lower than the seventh threshold value Tth11, the operation of the fan 13 can be suppressed from being wasted by stopping the fan 13.

[0100] Next, a second embodiment will be described. Hereinafter, differences from the previously described embodiment will be described in detail, and the same points will be appropriately omitted by assigning the same reference numerals to the same elements.

[0101] In the present embodiment, the control unit 100 can execute, as a printing operation, a normal printing operation as an example of the first printing operation and a half-speed printing operation as an example of the second printing operation. In the normal printing operation, the control unit 100 conveys the sheet S at the first conveyance speed, and in the half-speed printing operation, the control unit 100 conveys the sheet S at a second conveyance speed slower than the first conveyance speed. In the present embodiment, the second conveyance speed is approximately half of the first conveyance speed. The normal printing operation is substantially the same as the printing operation of the first embodiment described above.

[0102] When the fixing unit temperature T2 is less than the second threshold value Tth22, the control unit 100 executes a normal printing operation. When the fixing unit temperature T2 is greater than or equal to the second threshold value Tth22, instead of executing a cooling operation, the control unit 100 executes a half-speed printing operation.

[0103] In addition, when the corrected internal temperature T1 of the machine is greater than or equal to the fifth threshold value Tth41, the control unit 100 executes a half-speed printing operation. The corrected internal temperature T1 of the machine is an example of the fifth temperature based on the detection result of the internal temperature sensor ST1 of the machine. The fifth threshold value Tth41 is lower than the fourth threshold value Tth43. Also, the fifth threshold value Tth41 is lower than the threshold value Tth42 (see FIG. 5).

[0104] Next, the operation of the control unit 100 will be described with reference to a flowchart. When receiving a printing job, the control unit 100 executes the operation determination process shown in FIGS. 8 and 9.

[0105] As shown in FIG. 8, when receiving a printing job, the control unit 100 determines whether the outside temperature T3 of the machine is greater than or equal to the third threshold value Tth32 (S211). When the outside temperature T3 of the machine is less than the third threshold value Tth32 (S211, No), the control unit 100 determines whether the corrected internal temperature T1 of the machine is greater than or equal to the fourth threshold value Tth43 (S212). When the corrected internal temperature T1 of the machine is less than the fourth threshold value Tth43 (S212, No), the control unit 100 determines whether the corrected internal temperature T1 of the machine is greater than or equal to the fifth threshold value Tth41 (S213). When the corrected internal temperature T1 of the machine is less than the fifth threshold value Tth41 (S213, No), the control unit 100 determines whether the fixing unit temperature T2 is greater than or equal to the second threshold value Tth22 (S214).

[0106] When the fixing unit temperature T2 is less than the second threshold value Tth22 (S214, No), the control unit 100 executes a normal printing operation (S215). Thereafter, the control unit 100 determines whether the printing has ended (S216). If the printing has not ended (S216, No), the control unit 100 continues to execute the printing operation and returns to step S211 to execute the subsequent processing. If the printing has ended (S216, Yes), the control unit 100 ends the operation determination process.

[0107] On the other hand, when the corrected internal temperature T1 is equal to or higher than the fifth threshold value Tth41 in step S213 (Yes), or when the fixing unit temperature T2 is equal to or higher than the second threshold value Tth22 in step S214 (Yes), the control unit 100 executes a half-speed printing operation (S217). Thereafter, the control unit 100 determines whether printing has ended (S218). If printing has not ended (S218, No), the control unit 100 continues to execute the printing operation and proceeds to step S221 (see FIG. 9) described below to execute subsequent processing. If printing has ended (S218, Yes), the control unit 100 ends the operation determination process.

[0108] Also, when the external temperature T3 is equal to or higher than the third threshold value Tth32 in step S211 (Yes), or when the corrected internal temperature T1 is equal to or higher than the fourth threshold value Tth43 in step S212 (Yes), the control unit 100 executes a cooling operation (see FIG. 5). When the cooling operation ends, the control unit 100 executes a half-speed printing operation (S217).

[0109] Note that after starting the execution of the normal printing operation in step S215, when printing has not ended (S216, No) and the process returns to step S211, if the corrected internal temperature T1 becomes equal to or higher than the fifth threshold value Tth41 in step S213 (Yes), or if the fixing unit temperature T2 becomes equal to or higher than the second threshold value Tth22 in step S214 (Yes), and a half-speed printing operation is determined to be executed (S217), the control unit 100 executes the half-speed printing operation starting from the next sheet S of the sheet S being printed in the normal printing operation.

[0110] After starting the execution of the half-speed printing operation in step S217, if printing has not ended (S218, No), as shown in FIG. 9, the control unit 100 determines whether the outside temperature T3 is equal to or higher than the third threshold value Tth32 (S221). If the outside temperature T3 is lower than the third threshold value Tth32 (S221, No), the control unit 100 determines whether the corrected internal temperature T1 is equal to or higher than the fourth threshold value Tth43 (S222). If the corrected internal temperature T1 is lower than the fourth threshold value Tth43 (S222, No), the control unit 100 determines whether the corrected internal temperature T1 is equal to or lower than a threshold value Tth40 that is lower than the fifth threshold value Tth41 (S223). If the corrected internal temperature T1 is higher than the threshold value Tth40 (S223, No), the control unit 100 continues the execution of the half-speed printing operation (S227).

[0111] Also, if in step S223 the corrected internal temperature T1 is equal to or lower than the threshold value Tth40 (Yes), the control unit 100 determines whether the fixing unit temperature T2 is equal to or lower than a threshold value Tth21 that is lower than the second threshold value Tth22 (S224). If the fixing unit temperature T2 is higher than the threshold value Tth21 (S224, No), the control unit 100 continues the execution of the half-speed printing operation (S227).

[0112] Thereafter, the control unit 100 determines whether printing has ended (S228). If printing has not ended (S228, No), it returns to step S221 while continuing the execution of the printing operation and executes the subsequent processing. If printing has ended (S228, Yes), it ends the processing of operation determination (FIG. 8, END).

[0113] In step S224, when the fixing unit temperature T2 is equal to or lower than the threshold value Tth21 (S224, Yes), the control unit 100 determines to execute the normal printing operation (S225). The control unit 100 executes the normal printing operation starting from the next sheet S of the sheet S currently being printed in the half-speed printing operation. After step S225, the control unit 100 determines whether printing has ended (SS26). If printing has not ended (S226, No), it continues to execute the printing operation and returns to step S211 in FIG. 8 to execute subsequent processing. If printing has ended (S226, Yes), it ends the operation determination process (FIG. 8, END).

[0114] In step S221 of FIG. 9, when the external temperature T3 is equal to or higher than the third threshold value Tth32 (Yes), or in step S222, when the corrected internal temperature T1 is equal to or higher than the fourth threshold value Tth43 (Yes), the control unit 100 executes a cooling operation (see FIG. 5). When the cooling operation ends, the control unit 100 executes a half-speed printing operation (S227).

[0115] According to the above second embodiment, when the fixing unit temperature T2 is equal to or higher than the second threshold value Tth22 (FIG. 8, S214, Yes), the half-speed printing operation is executed (S217). Therefore, when the temperature of the heating unit 81 is high, a half-speed printing operation in which the heat of the fixing unit 80 easily moves to the sheet S can be executed. Thereby, it is possible to suppress the temperature of the fixing unit 80 from becoming too high. As a result, the fixing unit 80 can be used at a temperature below a predetermined temperature.

[0116] Also, when the corrected internal temperature T1 is equal to or higher than the fifth threshold value Tth41 (FIG. 8, S213, Yes), the half-speed printing operation is executed (S217). Therefore, when the temperature inside the housing 10 is high and the temperature of the heating unit 81 tends to be high, a half-speed printing operation in which the heat of the fixing unit 80 easily moves to the sheet S can be executed. Thereby, it is possible to suppress the temperature of the fixing unit 80 from becoming too high. As a result, the fixing unit 80 can be used at a temperature below a predetermined temperature.

[0117] In addition, in this embodiment, the half-speed printing operation is executed when the fixing unit temperature T2 is equal to or higher than the second threshold value Tth22, and when the corrected internal temperature T1 is equal to or higher than the fifth threshold value Tth41, but it is not limited thereto. For example, when the corrected internal temperature is equal to or higher than the fifth threshold value, the half-speed printing operation may be executed, and when the fixing unit temperature is equal to or higher than the second threshold value, the cooling operation may be executed.

[0118] Next, a third embodiment will be described. In this embodiment, in the standby state where the control unit 100 waits for the input of a print job, even when the corrected internal temperature T1 is equal to or higher than the sixth threshold value Tth12, if the rear cover 12 is open, the fan 13 is driven at a low speed.

[0119] Specifically, as shown in FIG. 10, when the corrected internal temperature T1 is equal to or higher than the sixth threshold value Tth12 (S13, Yes), the control unit 100 determines whether the rear cover 12 is open or closed (S14). When the rear cover 12 is closed (S14, No), the control unit 100 drives the fan 13 at a high speed (S16). On the other hand, when the rear cover 12 is open (S14, Yes), the control unit 100 drives the fan 13 at a low speed (S15).

[0120] According to the above-described third embodiment, even when the corrected internal temperature T1 is equal to or higher than the sixth threshold value Tth12 during standby, if the rear cover 12 is open, the fan 13 is driven at a low speed, so that the flow rate of air flowing into the housing 10 from the rear opening 10B can be reduced. As a result, it is possible to suppress the air heated by passing near the fixing unit 80 from flowing into the process unit 31, and thus it is possible to suppress the temperature rise of the process unit 31.

[0121] Although the embodiments have been described above, the image forming apparatus is not limited to the above embodiments, and can be appropriately modified and implemented as exemplified below.

[0122] In the above embodiment, when executing the printing operation, even when the rear cover 12 is closed, if the corrected internal temperature T1 is less than the first threshold value Tth1, the fan 13 is driven at a low speed, but it is not limited thereto. For example, when the cover is closed, the fan may always be driven at a high speed.

[0123] In the above embodiment, when executing the cooling operation, the fan 13 is always driven at a high speed, but it is not limited thereto. For example, when executing the cooling operation, the speed of the fan may be switched from high to low or gradually decreased according to the degree of cooling of the fixing unit.

[0124] In the above embodiment, as the second temperature based on the detection result of the fixing temperature sensor ST2, the fixing unit temperature T2 which is the measured value of the fixing temperature sensor ST2 is exemplified, but it is not limited thereto. For example, the second temperature may be a temperature obtained by correcting the measured value of the fixing temperature sensor.

[0125] In the above embodiment, as the third temperature based on the detection result of the outside temperature sensor ST3, the outside temperature T3 which is the measured value of the outside temperature sensor ST3 is exemplified, but it is not limited thereto. For example, the third temperature may be a temperature obtained by correcting the measured value of the outside temperature sensor. Note that the arrangement position of the outside temperature sensor ST3 described in the above embodiment is an example, and it may be arranged at a position different from the position described in the above embodiment.

[0126] In the above embodiment, as the fourth temperature based on the detection result of the internal temperature sensor ST1, the corrected internal temperature T1 which is a temperature obtained by correcting the measured value of the internal temperature sensor ST1 is exemplified, but it is not limited thereto. For example, the fourth temperature may be the measured value of the internal temperature sensor. The same applies to the fifth temperature. Note that the arrangement position of the internal temperature sensor ST1 described in the above embodiment is an example, and it may be arranged at a position different from the position described in the above embodiment. For example, the internal temperature sensor may be arranged in the developing cartridge 60A of the above embodiment.

[0127] In the above embodiment, as the first temperature based on the detection result of the temperature sensor, the corrected cabin temperature T1, which is the temperature obtained by correcting the measured value of the in-cabin temperature sensor ST1, is exemplified, but it is not limited thereto. For example, the first temperature may be the measured value of the in-cabin temperature sensor. Further, the first temperature may be the measured value of the fixing temperature sensor, or the temperature obtained by correcting the measured value of the fixing temperature sensor. Also, the first temperature may be the measured value of the outside-cabin temperature sensor, or the temperature obtained by correcting the measured value of the outside-cabin temperature sensor.

[0128] In the above embodiment, the corrected cabin temperature T1 was an example of the first temperature and also an example of the fourth temperature, but it is not limited thereto. That is, in the above embodiment, the first temperature and the fourth temperature were the same, but it is not limited to this and they may be different. The same applies to the first temperature and the fifth temperature.

[0129] In the above embodiment, the image forming apparatus 1 includes the second opening / closing sensor SC2 (opening / closing detection sensor), and the control unit 100 determines whether the rear cover 12 is open or closed based on the detection result of the second opening / closing sensor SC2, but it is not limited thereto. For example, in a configuration where the image forming apparatus does not include an opening / closing detection sensor, the control unit may be configured to determine that the rear cover is open when the user selects a printing mode such as discharging a sheet from the rear opening.

[0130] In the above embodiment, the in-cabin temperature sensor ST1, the fixing temperature sensor ST2, and the outside-cabin temperature sensor ST3 are exemplified as the temperature sensors, but it is not limited thereto. For example, as the temperature sensors, a configuration may be provided that includes only two or one of the in-cabin temperature sensor ST1, the fixing temperature sensor ST2, and the outside-cabin temperature sensor ST3 of the above embodiment. Also, as the temperature sensors, a configuration may be provided that further includes temperature sensors other than the temperature sensors ST1 to ST3 of the above embodiment.

[0131] In the above-described embodiment, the rear opening 10B and the rear cover 12 provided at the rear of the housing 10 were illustrated as the opening and the cover of the housing, but the present invention is not limited thereto. The cover is not limited to the cover provided at the rear of the housing as long as it allows the sheet on which the image has been formed to be discharged from the opening of the housing in the open state. For example, the opening and the cover of the housing may be an opening and a cover provided at the upper part of the housing, and the like.

[0132] In the above-described embodiment, only one fan 13 was illustrated, but the number of fans is arbitrary. That is, a plurality of fans may be provided. Further, the image forming apparatus may have a configuration in which, in addition to the fan according to the invention, that is, the fan that is driven at a low speed when the cover is open during the execution of the printing operation, for example, a second fan that takes air into the housing, and the like.

[0133] The configuration of the process unit described in the above embodiment is an example. For example, in the above embodiment, the exposure unit 40 exposes the surface of the photosensitive drum 51 by emitting a light beam to the photosensitive drum 51, but the present invention is not limited thereto. The exposure unit may include an exposure head having a plurality of arranged LEDs or the like, and may be configured to expose the surface of the photosensitive drum by irradiating the photosensitive drum with light from the LEDs.

[0134] Further, in the above embodiment, the transfer unit 70 is configured to include a transfer belt 73 that conveys the sheet S between the photosensitive drum 51, but the present invention is not limited thereto. For example, the transfer unit may be configured to include an intermediate transfer belt and a secondary transfer roller that transfers the toner image on the intermediate transfer belt to the sheet, instead of the transfer belt.

[0135] Further, in the above embodiment, the drum unit 50 is configured to include a photosensitive drum 51 that is a drum-shaped photoreceptor, but the present invention is not limited thereto. For example, the drum unit may be configured to include a belt-shaped photoreceptor.

[0136] Also, in the above-described embodiment, the process unit 31 includes the drum unit 50 and the developing cartridge 60 that is detachable from the drum unit 50. However, the present invention is not limited to this. For example, the process unit may include a unit in which the drum unit 50 and the developing cartridge 60 of the above-described embodiment are integrally formed in a non-detachable manner.

[0137] The configuration of the fixing unit described in the above-described embodiment is an example. For example, in the above-described embodiment, the heating unit 81 has the heating roller 81A. However, the present invention is not limited to this. The heating unit may have an endless belt that is heated by a heater instead of the heating roller. Also, in the above-described embodiment, the pressing unit 82 has an endless belt, a pressing pad, a holder, a belt guide, etc. However, the present invention is not limited to this. For example, the pressing unit may be a pressing roller having a core metal and an elastic layer formed around the core metal.

[0138] In the above-described embodiment, the image forming apparatus 1 is a color printer. However, the present invention is not limited to this. For example, the image forming apparatus may be a monochrome printer. Also, the image forming apparatus is not limited to a printer. For example, it may be a copying machine, a multifunction machine, or the like.

[0139] Each element described in the above-described embodiment and the modified example may be implemented in any combination.

Description of Reference Numerals

[0140] 1 Image forming apparatus 10 Housing 10B Rear opening 12 Rear cover 13 Fan 31 Process unit 80 Fixing unit 81 Heating unit 100 Control unit S Sheet

Claims

1. A housing having an opening, A cover for opening and closing the opening, A process unit for transferring a toner image onto a sheet, A fixing unit having a heating unit for heating the sheet, and fixing the toner image transferred by the process unit onto the sheet, the fixing unit being disposed between the closed cover and the process unit, A discharge tray for discharging the sheet on which the toner image has been fixed by the fixing unit with the cover closed, A fan for discharging the air inside the housing when driven, A control unit capable of executing a printing operation for forming an image on a sheet, and The cover is configured such that when open, the sheet on which the toner image has been fixed by the fixing unit is discharged onto the cover through the opening, When the control unit executes a printing operation, When the cover is closed and the sheet on which the toner image has been fixed by the fixing unit is discharged to the discharge tray, the fan is driven at a first speed, When the cover is open and the sheet on which the toner image has been fixed by the fixing unit is discharged onto the cover through the opening, the fan is driven at a second speed slower than the first speed. An image forming apparatus characterized by this.

2. Equipped with a temperature sensor, When the control unit executes a printing operation, even when the cover is closed, if the first temperature based on the detection result of the temperature sensor is less than a first threshold value, the fan is driven at the second speed. The image forming apparatus according to claim 1, characterized by this.

3. The first temperature is a temperature obtained by correcting the measured value of the temperature sensor. The image forming apparatus according to claim 2, characterized by this.

4. Equipped with a temperature sensor, The control unit, Based on the detection result of the temperature sensor, is capable of executing a cooling operation that prohibits the execution of the printing operation and cools the fixing unit, When executing the cooling operation, the fan is driven at the first speed. The image forming apparatus according to claim 1, characterized by this.

5. The temperature sensor includes a fixing temperature sensor that detects the temperature of the heating unit, When the second temperature based on the detection result of the fixing temperature sensor is equal to or higher than a second threshold value, the control unit executes the cooling operation. The image forming apparatus according to claim 4, characterized by this.

6. The temperature sensor includes a fixing temperature sensor that detects the temperature of the heating unit, The control unit, As the printing operation, it is possible to execute a first printing operation for conveying a sheet at a first conveyance speed and a second printing operation for conveying the sheet at a second conveyance speed slower than the first conveyance speed. The image forming apparatus according to claim 4, wherein the second printing operation is executed when a second temperature based on a detection result of the fixing temperature sensor is equal to or higher than a second threshold value.

7. The temperature sensor includes an external temperature sensor that detects the temperature outside the housing. The control unit executes the cooling operation when a third temperature based on a detection result of the external temperature sensor is equal to or higher than a third threshold value, according to any one of claims 4 to 6. The image forming apparatus described.

8. The temperature sensor includes an internal temperature sensor that detects the temperature inside the housing. The control unit executes the cooling operation when a fourth temperature based on a detection result of the internal temperature sensor is equal to or higher than a fourth threshold value, according to any one of claims 4 to 7. The image forming apparatus described.

9. The temperature sensor includes an internal temperature sensor that detects the temperature inside the housing. The control unit As the printing operation, it is possible to execute a first printing operation for conveying a sheet at a first conveyance speed and a second printing operation for conveying the sheet at a second conveyance speed slower than the first conveyance speed. The image forming apparatus according to any one of claims 4 to 8, wherein the second printing operation is executed when a fifth temperature based on a detection result of the internal temperature sensor is equal to or higher than a fifth threshold value.

10. An open / close detection sensor for detecting the opening and closing of the cover is provided. The control unit determines whether the cover is open or closed based on a detection result of the open / close detection sensor, according to any one of claims 1 to 9. The image forming apparatus described.

11. A temperature sensor is provided. In a standby state where the control unit waits for an input of a print job, When a first temperature based on a detection result of the temperature sensor is equal to or higher than a sixth threshold value, the fan is driven at the first speed. When the first temperature is less than the sixth threshold value and equal to or higher than a seventh threshold value lower than the sixth threshold value, the fan is driven at the second speed. The image forming apparatus according to claim 1, wherein the fan is stopped when the first temperature is less than the seventh threshold value.

12. The image forming apparatus according to claim 11, characterized in that, even when the first temperature is equal to or higher than the sixth threshold value, if the cover is open, the control unit drives the fan at the second speed.

Images