JP6261545B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a fixing machine for fixing a developer image on a sheet and a cooling method for a sheet on which an image is formed in an image forming apparatus such as a copying machine, a printer, or a facsimile employing an electrophotographic system.

  Conventionally, in an image forming apparatus using an electrophotographic system, a sheet having a developer image formed on a surface with a developer such as toner is nipped and conveyed by a pair of fixing rollers composed of a heating roller and a pressure roller of a fixing machine, Fix by heating and pressing.

In such an image forming apparatus, when a sheet narrower than the maximum width of the fixing roller pair of the fixing device is nipped and conveyed, heat is not absorbed by the sheet in a portion where the sheet of the fixing roller pair does not pass. However, the temperature rises and the temperature distribution becomes non-uniform.
In order to make the temperature distribution of the fixing roller pair uniform, a fan that controls a fan that cools the fixing roller pair according to the width of the sheet is disclosed. (See Patent Document 1)
In addition, when sheets on which images are formed are discharged and overlapped with heat, the overlapped sheets may adhere to each other due to the softened developer. When the attached sheets are separated from each other, an image or a sheet formed on the sheet may be damaged.
In view of this, a sheet is disclosed in which air is blown from a fan onto a sheet that has been heated and pressurized by a fixing machine and then cooled. (See Patent Document 2)
JP 2007-219032 A JP 2014-126763 A

However, when moisture contained in the sheet evaporates due to heating of the sheet during fixing, the surrounding air is humidified. When the humidified air moves to the periphery of the laser scanner as the exposure device inside the image forming apparatus by the airflow generated by the fan, there is a problem that condensation occurs on the laser scanner depending on the environment around the image forming apparatus.
If dew condensation occurs in the laser scanner, especially at the laser emission part, the laser scanner cannot output the amount of light necessary to form an electrostatic latent image on the photosensitive drum as the image carrier, causing problems during image formation. It may cause.

  An object of the present invention is to prevent the formation of condensation in an exposure apparatus and coolly form an image when a fixing machine or a sheet after image formation is cooled.

In order to achieve the above object, the present invention provides:
An image forming apparatus,
Exposure means for exposing the image carrier in accordance with image data to form an electrostatic latent image;
Developing means for developing an image carrier having an electrostatic latent image formed thereon by the exposure means into a toner image;
Transfer means for transferring the toner image developed by the developing means to a recording medium;
Fixing means for fixing the toner image transferred to the recording medium by the transfer means to the recording medium by heat;
An air blower for generating an airflow toward the exposure unit by air around the fixing unit;
Temperature detecting means for detecting the temperature inside the image forming apparatus;
When the temperature detection means detects a temperature in a first temperature range less than a predetermined temperature, the fixing means is set to a first set temperature, and the temperature detection means detects a temperature in a second temperature range equal to or higher than the predetermined temperature. A temperature setting means for setting the fixing means to a second set temperature lower than the first set temperature,
When the temperature detecting means detects the temperature in the first temperature range, the blowing by the blowing means is stopped, and when the temperature detecting means detects the temperature in the second temperature range, the blowing by the blowing means Control means for performing
Thus, an image forming apparatus is configured.

  According to the image forming apparatus of the present invention, when the fixing machine and the sheet after image formation are cooled, it is possible to prevent the occurrence of condensation in the exposure apparatus and form an image stably.

1 is a schematic configuration diagram of an image forming apparatus according to the present invention. Control block diagram of image forming apparatus Control block diagram of image forming unit Explanatory drawing of air movement in the machine by a conventional image forming apparatus Explanatory drawing of the movement of air in the machine by the image forming apparatus of the present invention Example of table used for fan control Flow chart of control in embodiment 1 An example of a table used for fan control in consideration of the target temperature control temperature for fixing Flow chart of control in embodiment 2 Flow chart of control in embodiment 3 Flow chart of control in embodiment 4

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention, and includes an image reading apparatus 200 and an image forming apparatus 100.

In FIG. 1, the image reading apparatus 200 includes an image reading unit 210 that reads an image of a document, and a document feeding unit 220 that feeds a document D to the image reading unit 210.
The image forming apparatus 100 includes a sheet feeding unit 10, an image forming unit 20, a fixing unit 30, and a sheet discharge unit 40 in order from the bottom to the top. A sheet refeeding unit 50 is provided on the right side of the image forming unit 20 and the fixing unit 30.

  In the sheet feeding unit 10, the sheets S stacked on the feeding cassette 11 and the manual feed tray 17 are fed to the image forming unit 20. The sheet S stored in the feeding cassette 11 is fed to the separation roller pair 13 as the pickup roller 12 rotates. When the sheet S is double-fed, it is separated into one sheet by a separating roller pair 13 composed of a normal rotation roller and a reversing roller, and is supplied to a feeding path PS1 indicated by a solid line.

Next, the sheet S is conveyed to the registration roller pair 16 by the feeding roller pair 15. Here, the skew of the sheet S is corrected by causing the leading edge of the sheet S to follow the nip of the registration roller pair 16 that has stopped rotating. When the sheet S is fed from the multi-feed tray 17, the sheet is separated into one sheet by the supply roller 18a and the separation pad 18b. Then, the sheet S is supplied to the feeding roller pair 15 by the supply roller pair 19 and conveyed to the registration roller pair 16 so that the skew of the sheet S is corrected.
The sheet whose skew has been corrected is conveyed to the image forming unit 20 by the registration roller pair 16 rotating at a predetermined timing.

  In the image forming unit 20, the surface of the photosensitive drum 21 is uniformly charged by the charging roller 22. When the laser beam corresponding to the image information is irradiated from the laser unit 23, the charge charged by the charging roller 22 is removed from the portion of the photosensitive drum 21 irradiated with the laser beam, and the electrostatic corresponding to the image information is removed. A latent image is formed. The electrostatic latent image formed here is visualized as a developer image by the developer attached by the developing roller 24 of the developing device.

  The developer image is conveyed to the transfer nip portion N1 by the rotation of the photosensitive drum 21. In synchronization with this timing, the sheet S is conveyed from the registration roller pair 16 to the transfer nip portion N1. The conveyed sheet S is nipped and conveyed between the photosensitive drum 21 and the transfer roller 25 in the transfer nip portion N1. At this time, the developer image formed on the photosensitive drum 21 by the bias voltage application from the transfer roller 25 is transferred to the sheet S. The laser light emitted from the laser unit 23 is controlled based on image data transmitted from the image reading apparatus 200 or the host PC 1.

  Next, the sheet S on which the developer image is formed is conveyed to the fixing unit 30. The fixing unit 30 includes a heat source such as a halogen lamp (not shown), a fixing roller 31, and a pressure roller 32. The fixing roller 31 is made of a material such as aluminum and is heated to a predetermined temperature by a heat source. The pressure roller 32 is installed so as to be in contact with the fixing roller 31 and pressurize with a predetermined pressure, and forms a fixing nip portion N2.

  The sheet S on which the developer image is formed is sent to the fixing nip portion N2 and is nipped and conveyed by the fixing roller 31 and the pressure roller 32. At this time, the developer image is fixed on the sheet S by being heated and pressurized. In addition to the heating roller system in which the fixing unit 30 is heated by the fixing roller 31, the pressure roller 32 in FIG. 3 presses a heat source such as the ceramic heater 33 through the endless film so that the fixing nip N2 An on-demand fixing method in which the sheet S is nipped and conveyed while being nipped and conveyed at the nip portion N2 may be used.

Next, the sheet S on which the developer image is fixed is conveyed to the sheet discharge unit 40 and discharged to the discharge tray 42 by the discharge roller pair 41.
When images are formed on both sides of the sheet S, the discharge roller before the trailing edge of the sheet S passes through the discharge roller pair 41 when the sheet S on which the image is formed on the first surface is conveyed by the discharge roller pair 41. The pair 41 is temporarily stopped, and the discharge roller pair 41 is further rotated in the reverse direction, whereby the sheet S is reversed and conveyed to the sheet refeeding unit 50.
The sheet S conveyed to the sheet re-feeding unit 50 is conveyed on a re-feed path PS2 indicated by a broken line by re-feed roller pairs 51a and 51b, and is conveyed to the registration roller pair 16 by a re-feed roller pair 51c. . After the skew is corrected by the registration roller pair 16, the back surface is conveyed to the transfer nip portion N 1, whereby a developer image is formed on the second surface of the sheet S. Thereafter, the developer image is fixed on the sheet S by being conveyed through the fixing nip portion N2 in the same manner as when the image is formed on the front surface. Is discharged.

  In addition, an environmental sensor S1 is installed inside the image forming apparatus 100, and the temperature and humidity in the image forming apparatus can be detected as electrical signals. A thermistor is generally known as the temperature detecting means, and a capacitance sensor is generally known as the humidity detecting means. In this embodiment, a combined sensor is provided.

FIG. 2 is a control block diagram of the image forming system of FIG. In FIG. 2, 101 is a CPU as a control means. The CPU 101 includes a RAM 102 that is used as a storage area for input data, a working storage area, and the like, and a ROM 103 that stores programs such as control procedures. The CPU 101 is connected to the host PC 1 via the external interface 2 and performs reception of image data, transmission of device status, and the like.
The CPU 101 includes an image reading device control unit 120 that controls a document reading operation and a document conveying operation by the reading scanning unit 250, an image signal processing unit 110 that processes an image signal from the image reading device control unit 120 or the host PC 1, and an image. An image forming apparatus control unit 130 that forms an image on a sheet in accordance with an image signal sent from the signal processing unit 110, and an operation / display unit 140 that performs setting of the main body and the like and displays a message to the user.

FIG. 3 is a block diagram of the image forming apparatus control unit 130 in FIG. In FIG. 3, the image forming apparatus control unit 120 includes a RAM 122 used as a storage area for input data and a working storage area, and a ROM 123 storing a program such as a control procedure, as in the control block diagram of the image forming system in FIG. The CPU 121 is provided as control means.
The CPU 121 has a voltage control unit U1 for applying a voltage to the charging roller 22, the developing roller 24, the transfer roller 24, and the ceramic heater 33 as a heat source via the I / O port 124, and the photosensitive drum 21 in FIG. A laser unit 23 for exposing the surface, a common drive motor driver D1, and a fan motor driver D2 are connected.
The common drive motor driver D1 controls the operation of the common drive motor M1 as a drive source for rotating the photosensitive drum 21, the developing roller 24, and the transfer roller 25. The fan motor driver D2 controls the operation of the fan motor M2 that drives the cooling fan 60 that cools the fixing unit 30 and the sheet S in FIG.
An environmental sensor S1 is connected to the CPU 121, and the temperature and humidity in the image forming apparatus can be detected. The temperature and humidity in the image forming apparatus may be determined from the detection result of the environment outside the apparatus in addition to directly detecting the environment inside the apparatus.

FIG. 4 is a view for explaining the air flow in the apparatus in the conventional image forming apparatus. In FIG. 4, an arrow A indicates the flow of air.
In order to cool the sheet S that has been heated and pressurized in the fixing unit 30 and the fixing unit 30, the cooling fan 60 always supplies the outside air to the fixing unit 30 and the sheet S with a constant air volume. Blowing. When the sheet S is heated by the fixing unit 30, the moisture contained in the sheet S is released as water vapor, and the temperature and humidity of the air around the fixing unit 30 increases.

  When high-humidity air reaches the laser scanner 23 serving as an exposure apparatus due to the airflow generated by the cooling fan 60, condensation may occur in the laser scanner 23. In particular, when dew condensation occurs on the surface of the dustproof member 23a formed of a transparent member provided in the laser output section of the laser scanner 23, an image defect such as a decrease in the density of the output image may occur. This is because the amount of laser light emitted from the laser scanner 23 to the photosensitive drum 21 decreases when condensation occurs on the surface of the dust-proof member 23a.

FIG. 5 is a view for explaining the air flow in the apparatus in the image forming apparatus according to the present embodiment. Arrow B indicates the flow of air.
The air volume of the cooling fan 60 is adjusted by the CPU 121 of FIG. 3 controlling the fan motor M2 via the fan motor driver D1 of FIG. The air volume of the cooling fan 60 is adjusted so that the generated air current is blocked by each component of the image forming apparatus 100 and does not reach the laser scanner 23. In this embodiment, the output is adjusted to half speed (50%) for full speed (100%) driving.

6 is a table showing drive control of the cooling fan 60 in FIG. 5 with respect to the output result of the environment sensor S1 in FIG. The environmental conditions are divided into three regions, region A, region B, and region C, depending on the ease of condensation due to temperature and humidity. The CPU 121 in FIG. 3 collates the output of the environmental sensor S1 in FIGS. 3 and 5 with the table in FIG. 6, and the cooling of FIG. The control of the fan 60 is changed.
As the environmental conditions, the lower the temperature and the higher the humidity, the more likely condensation occurs in the apparatus. Therefore, the contents of the table are set so as to reduce the air volume of the cooling fan 60 in the low temperature region or the high humidity region.

  Based on the flowchart of FIG. 7, the cooling method in a present Example is demonstrated. The processing in FIG. 7 is implemented by the CPU 121 in FIG. 3 executing the program stored in the ROM 123 in FIG.

  When a print job is transmitted as a print command from the host PC in FIG. 1 to the image forming apparatus 100 in FIG. 1, the CPU 121 in FIG. 3 rotates the common drive motor via the common drive motor driver D1 in FIG. A voltage is applied to the ceramic heater of FIG. 3 via the voltage control unit U1 of FIG. 3 to perform heating. (Step S701)

Next, temperature and humidity are detected by the environmental sensor S1 in FIG. (Step S702)
Next, the temperature and humidity environmental conditions detected in step S702 are collated with the table of FIG. (Step S703)

When the environmental condition is in the region A or the region B from the comparison result of the temperature and humidity, the CPU 121 in FIG. 3 controls the fan motor M2 in FIG. 3 via the fan motor driver D2 in FIG. The cooling fan 60 is driven at half speed. (Step S704)
When the environmental condition is in the region C, the CPU 121 in FIG. 3 drives the cooling fan 60 in FIG. 5 at full speed. (Step S705)

  Thereafter, a printing operation for forming an image on the sheet S is performed. (Step S706)

  When the print job is finished, the operation of the fixing unit 30 is stopped (step S708), the operation of the cooling fan 60 is stopped (step S709), and the operation is finished.

  If the print job has not been completed, the process returns to step S702 to continue processing.

  In order to cool the sheet S heated and pressurized in the fixing unit 30 in FIG. 5 and the fixing unit 30 in FIG. 5, it is desirable to always drive the cooling fan 60 in FIG. 5 at full speed. However, in environmental conditions where condensation is likely to occur, the cooling fan 60 is driven at half speed to prevent condensation from occurring in the laser scanner 23 of FIG. Condensation is likely to occur under low temperature conditions. Therefore, even if the cooling fan 60 is driven at half speed at this time, the air volume necessary for cooling the fixing unit 30 and the sheet S can be maintained.

  In this embodiment, the operation of the cooling fan 60 is controlled based on the detection results of both temperature and humidity. However, it is also possible to control using the detection result of only temperature or humidity. is there.

  In addition, the environmental condition area is divided into three areas, area A, area B, and area C, and the cooling fan 60 is controlled in two stages of full-speed driving and half-speed driving. is there.

  In this embodiment, the image forming apparatus that transfers the developer image from the photosensitive drum to the sheet has been described. However, the developer image is transferred from the photosensitive drum to the intermediate transfer belt, and further from the intermediate transfer belt to the sheet. The present invention can also be applied to an image forming apparatus that employs a method of transferring a developer image to the head.

  As described above, in the image forming apparatus of the present invention, the driving control of the cooling fan 60 is changed based on the environmental conditions so that the air volume is reduced in the environmental conditions where condensation is likely to occur. For this reason, the air humidified in the fixing unit 30 does not reach the laser scanner 23. Therefore, it is possible to prevent dew condensation from occurring in the laser scanner as the exposure apparatus.

In this embodiment, the set temperature of the fixing unit 30 is switched according to the environmental conditions inside the image forming apparatus in the image forming apparatus of the first embodiment.

  Hereinafter, a detailed description will be given with reference to FIG. 8, and parts having the same configurations as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  If the set temperature of the ceramic heater 33 is the same regardless of the environmental conditions inside the image forming apparatus, a region where condensation is likely to occur can be divided as in the environmental table of FIG. However, in consideration of the curling of the sheet S, the fixing property of the developer to the sheet S, and the like, the CPU 121 sets the set temperature of the ceramic heater 33 to be lower as the temperature in the image forming apparatus is higher, and the temperature is lower. The set temperature of the ceramic heater 33 is set higher. When the set temperature of the ceramic heater 33 is increased, the amount of water vapor generated from the sheet S when the sheet S passes through the fixing nip portion N2 increases and condensation easily occurs. Therefore, in addition to the temperature and humidity inside the image forming apparatus, the sheet It is necessary to control the cooling fan 60 in consideration of the influence of water vapor generated from S.

  FIG. 8 is an example of an environment table used for control for switching the air volume of the cooling fan 60 based on the temperature of the ceramic heater 33 set according to the environmental conditions inside the image forming apparatus.

In this embodiment, the environmental conditions are divided into three regions, region D, region E, and region F, according to temperature and humidity, and the temperature of the ceramic heater 33 is set for each region.
In the region D, the set temperature of the ceramic heater 33 is set to 190 ° C. higher than other environmental regions in order to satisfy the fixing property in a low temperature environment. For this reason, the amount of water vapor generated from the sheet S increases and condensation tends to occur. However, in the region D, the temperature in the image forming apparatus is low and the sheet S is easily cooled. For this reason, it is an environment in which curling is unlikely to occur without actively blowing air and cooling the sheet S. Therefore, it is possible to prevent condensation from occurring by stopping the cooling fan 60.

  The region E is an environment between the regions D and F, and the set temperature of the ceramic heater 33 is 180 ° C. In the region E, the temperature of the sheet S and the amount of water vapor generated from the sheet S are intermediate between the region D and the region F. In the region E, by driving the cooling fan 60 at half speed (50%), it becomes possible to cool the sheet by blowing air and prevent the occurrence of condensation while suppressing the occurrence of curling.

    In the region F, the inside of the image forming apparatus is a high temperature and high humidity environment, and the set temperature of the ceramic heater 33 is 150 ° C. Region F is an environmental condition in which the temperature in the image forming apparatus is high and condensation is unlikely to occur, and the set temperature of the ceramic heater 33 is low and the amount of water vapor generated from the sheet S is small. Therefore, it is possible to prevent the occurrence of condensation even if the cooling fan 60 is rotated at full speed.

  Based on the flowchart of FIG. 9, the cooling method in a present Example is demonstrated. Note that a description of the same parts as those in the flowchart of FIG. 7 is omitted.

  Based on the flowchart of FIG. 9, the cooling method in a present Example is demonstrated. The processing in FIG. 9 is implemented by the CPU 121 in FIG. 3 executing the program stored in the ROM 123 in FIG.

  When a print job is transmitted as a print command from the host PC in FIG. 1 to the image forming apparatus 100 in FIG. 1, the CPU 121 in FIG. 3 detects temperature and humidity by the environment sensor S1 in FIG. (Step S1101)

  Next, the environmental conditions of temperature and humidity detected in step S1101 are collated with the table of FIG. (Step S1102)

  When the environmental condition is in the region E from the comparison result of the temperature and humidity, the CPU 121 in FIG. 3 rotates the common drive motor via the common drive motor driver D1 in FIG. 3 and the voltage control unit U1 in FIG. Then, the ceramic heater 33 in FIG. 3 is heated according to the environmental conditions of the temperature and humidity detected in step S1101.

  The target temperature is set to 190 ° C. (step S1103) if the environmental condition is D, 180 ° C. (step S1104) if it is E, and 150 ° C. (step S1105) if it is F. The heating operation is performed up to the specified temperature.

Next, the cooling fan 60 of FIG. 5 is driven by controlling the fan motor M2 of FIG. 3 via the fan motor driver D2 of FIG.
When the environmental condition is the region D, the driving of the cooling fan 60 is stopped (step S1106). When the environmental condition is the region E, the driving is performed at half speed (step S1107), and when the region is the region F, the driving is performed at full speed (step S1108).

  Thereafter, a printing operation for forming an image on the sheet S is performed (step S1109).

  When the print job is finished, the operation of the fixing unit 30 is stopped (step S1111), the operation of the cooling fan 60 is stopped (step S1112), and the operation is finished. If the print job has not been completed, the process returns to step S1109 to continue processing.

  In this embodiment, the operation of the cooling fan 60 is controlled based on the detection results of both temperature and humidity. However, it is also possible to control using the detection result of only temperature or humidity. is there.

  In addition, the environmental condition region is divided into three regions, region D, region E, and region F, and the cooling fan 60 is controlled in three stages of full speed drive, half speed drive, and stop, but it may be further divided and controlled. Is possible.

  As described above, in the image forming apparatus of the present invention, the air volume is reduced according to the environmental conditions and the temperature of the ceramic heater 33 set based on the environmental conditions in the case of the environmental conditions where condensation is likely to occur. The drive control of the cooling fan 60 is changed. For this reason, the air humidified in the fixing unit 30 does not reach the laser scanner 23. Therefore, it is possible to prevent dew condensation from occurring in the laser scanner as the exposure apparatus.

  In this embodiment, the cooling method is changed according to the number of printed sheets with respect to the image forming apparatus described in the first embodiment.

  Based on the flowchart of FIG. 10, the cooling method in a present Example is demonstrated. Note that a description of the same parts as those in the flowchart of FIG. 7 is omitted. In addition, the same reference numerals are given to portions having the same configuration as that of the first embodiment, and the description thereof is omitted.

  After the image forming apparatus 100 in FIG. 1 receives a print command from the host PC in FIG. 1, the CPU 121 in FIG. 3 starts the operation of the fixing unit 30 in FIG. 1 (S801), and the environment sensor S1 in FIG. The humidity is detected (step S802).

  Next, the CPU 121 in FIG. 3 determines the number of prints of the print job transmitted from the host PC in FIG. 1 (step S804).

  If the number of printed sheets is less than 50, the process proceeds to step S805 to determine the environment. If the environmental condition is area A in the table of FIG. 6, the cooling fan 60 of FIG. 1 is driven at half speed (step S806). If the condition is region B or region C, the cooling fan 60 of FIG. 1 is driven at full speed (step S806).

  If the number of printed sheets is 50 or more, the process proceeds to step S808 to determine the environment. If the environmental condition is area A or area B in the table of FIG. 6, the cooling fan 60 of FIG. 1 is driven at half speed (step S806). ) If the environmental condition is region C, the cooling fan 60 of FIG. 1 is driven at full speed (step S806).

  Thereafter, a printing operation for forming an image on the sheet S is performed. (Step S810)

  When the print job is finished, the operation of the fixing unit 30 is stopped (step S812), the operation of the cooling fan 60 is stopped (step S813), and the operation is finished. If the print job has not been completed, the process returns to step S810 to continue processing.

  By performing the above control, it is possible to prevent dew condensation from occurring in the laser scanner as the exposure apparatus even when the number of print jobs is large and the humidity in the apparatus tends to increase.

  In this embodiment, the image forming apparatus described in the first embodiment is described in which the cooling method is changed depending on the number of printed sheets. However, the image forming apparatus described in the second embodiment can be similarly combined and implemented. is there.

  In this embodiment, the cooling method is changed with respect to the image forming apparatus described in the first embodiment depending on the size of the sheet on which the image is formed.

  Based on the flowchart of FIG. 11, the cooling method in a present Example is demonstrated. Note that a description of the same parts as those in the flowcharts of FIGS. 7 and 10 is omitted. In addition, the same reference numerals are given to portions having the same configuration as that of the first embodiment, and the description thereof is omitted.

  After the image forming apparatus 100 in FIG. 1 receives a print job as a print command from the host PC in FIG. 1, the CPU 121 in FIG. 3 starts the operation of the fixing unit 30 in FIG. 1 (S901), and the environment sensor in FIG. Temperature and humidity are detected in S1 (step S902).

  In step S903, the environmental condition is determined. If the environmental condition is in the area A or B in the table of FIG. 6, the sheet width is determined in step S904.

  The CPU 121 in FIG. 3 determines the width of the sheet S on which an image is to be formed from the contents of the print job transmitted from the host PC in FIG. When the width of the sheet S exceeds the letter size of 279 mm, the CPU 121 in FIG. 3 drives the cooling fan 60 in FIG. 1 at half speed (step S905).

  If it is the region C in the environmental condition determination in step S903, and if the width of the sheet S is 279 mm or less of the letter size in the sheet width determination in step S904, the process proceeds to step S906, and the CPU 121 in FIG. The cooling fan 60 is driven at full speed.

  When the width of the sheet S in the sheet passing direction is narrower than the sheet passing region, the area where the sheet S contacts the fixing nip N2 is reduced in the fixing unit 30 of FIG. 1, and the water vapor generated by heating the sheet S is also reduced. . Therefore, even when the cooling fan 60 is driven at full speed, no condensation occurs in the laser scanner 23.

  By performing the above control, it is possible to prevent dew condensation from occurring in the laser scanner as the exposure apparatus regardless of the size of the sheet on which the image is formed.

In the present exemplary embodiment, the description has been given of the image forming apparatus described in the first exemplary embodiment in which the cooling method is changed depending on the size of the sheet on which the image is formed. However, the present exemplary embodiment can be combined with other exemplary embodiments. is there.

1 Host PC
20 Image forming unit 23 Laser scanner 23a Dust-proof member 30 Fixing unit 40 Sheet discharging unit 50 Sheet refeeding unit 60 Cooling fan 100 Image forming apparatus 101 CPU
102 RAM
103 ROM
110 Image signal controller 120 Image reader controller 121 CPU
122 RAM
123 ROM
124 I / O port 130 Image forming apparatus control unit 140 Operation / display unit D1 Common drive motor driver D2 Fan motor driver M1 Common drive motor M2 Fan motor S1 Environmental sensor

Claims (5)

An image forming apparatus,
Exposure means for exposing the image carrier in accordance with image data to form an electrostatic latent image;
Developing means for developing an image carrier having an electrostatic latent image formed thereon by the exposure means into a toner image;
Transfer means for transferring the toner image developed by the developing means to a recording medium;
Fixing means for fixing the toner image transferred to the recording medium by the transfer means to the recording medium by heat;
An air blower for generating an airflow toward the exposure unit by air around the fixing unit;
Temperature detecting means for detecting the temperature inside the image forming apparatus;
When the temperature detection means detects a temperature in a first temperature range less than a predetermined temperature, the fixing means is set to a first set temperature, and the temperature detection means detects a temperature in a second temperature range equal to or higher than the predetermined temperature. A temperature setting means for setting the fixing means to a second set temperature lower than the first set temperature,
When the temperature detecting means detects the temperature in the first temperature range, the blowing by the blowing means is stopped, and when the temperature detecting means detects the temperature in the second temperature range, the blowing by the blowing means Control means for performing
An image forming apparatus comprising: An image forming apparatus,
Exposure means for exposing the image carrier in accordance with image data to form an electrostatic latent image;
Developing means for developing an image carrier having an electrostatic latent image formed thereon by the exposure means into a toner image;
Transfer means for transferring the toner image developed by the developing means to a recording medium;
Fixing means for fixing the toner image transferred to the recording medium by the transfer means to the recording medium by heat;
An air blower for generating an airflow toward the exposure unit by air around the fixing unit;
Temperature detecting means for detecting the temperature inside the image forming apparatus;
When the temperature detection means detects a temperature in a first temperature range less than a predetermined temperature, the fixing means is set to a first set temperature, and the temperature detection means detects a temperature in a second temperature range equal to or higher than the predetermined temperature. A temperature setting means for setting the fixing means to a second set temperature lower than the first set temperature,
When the temperature detection means detects the temperature of the first temperature range, the control means for reducing the air volume by the blower means than when the temperature detection means detects the temperature of the second temperature range;
An image forming apparatus comprising:   3. The image according to claim 1, wherein the control unit changes a driving condition of the blowing unit so as to reduce an air volume in accordance with an increase in a set temperature of the fixing unit. Forming equipment. A print number detecting unit for detecting the number of prints of the print job;
The said control means changes the drive condition of the said ventilation means so that an air volume may reduce according to the said number of printed sheets increasing, The said any one of Claim 1 thru | or 3 characterized by the above-mentioned. Image forming apparatus. A sheet size detecting means for detecting the size of the sheet forming the image;
The said control means changes the drive condition of the said ventilation means so that an air volume may reduce according to the said sheet | seat size becoming large, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Image forming apparatus.

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