JP2018138953A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable image formation without generating dew condensation in an image forming apparatus 100 comprising image forming means 20 that includes an exposure device 23 and forms a toner image on a recording medium S, and fixing means 30 that thermally fixes the toner image on the recording medium formed by the image forming means.SOLUTION: An image forming apparatus comprises: first temperature detection means S1 that detects the temperature of air inside an apparatus body 100A accommodating image forming means 20 and fixing means 30; humidity detection means S1 that detects the humidity of the inside air; second temperature detection means 23b that detects the temperature of a dust-proof member 23a of an exposure device; air blowing means 60 that blows air toward a recording medium after passing through the fixing means 30; an air channel through which the air after being blown toward the recording medium enters the inside of the apparatus body 100A; and control means 130 that controls the volume of air blown from the air blowing means 60 on the basis of results of detection performed respectively by the first temperature detection means S1, second temperature detection means 23b, and humidity detection means S1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to determination of a dew condensation occurrence case of an exposure apparatus in an apparatus main body and an optimum dew condensation countermeasure according to the dew condensation occurrence case in an image forming apparatus such as a copying machine, a printer, or a facsimile employing an electrophotographic system.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system, a sheet as a recording medium having a developer image formed on a surface with a developer such as toner is formed by a pair of fixing rollers including a heating roller and a pressure roller of a fixing machine. It is nipped and conveyed and fixed by heating and pressing.

  In such an image forming apparatus, when a sheet having a width smaller than the maximum fixable 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. Therefore, the temperature rises more than the part through which the sheet passes, and the temperature distribution along the length (width) of the fixing roller pair 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 sheet non-passing portion of the fixing roller pair according to the width of the sheet is disclosed (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, an apparatus is disclosed in which air is blown from a fan onto a sheet that has been heated and pressurized by a fixing machine to cool the sheet (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 main body by the airflow generated by the fan, condensation may occur on the laser scanner depending on the environment around the image forming apparatus. There is.

  When 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, and this is not good for image formation May be caused.

  In general, condensation of the image forming apparatus may occur in the apparatus body when the apparatus is suddenly moved from a cold room to a warm room. Condensation in this case and condensation due to steam generated by heating the sheet at the time of fixing described above differ in the case where condensation occurs in the same exposure apparatus, and the source and characteristics of condensation are also different. For this reason, there is a problem that the dew condensation is erroneously detected or cannot be detected, and the same dew condensation measure is taken regardless of the case where the dew condensation occurs.

  Accordingly, an object of the present invention is to prevent the occurrence of condensation and enable stable image formation.

  In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes an image forming unit that has an exposure device and forms a toner image on a recording medium, and is formed on the recording medium by the image forming unit. An image forming apparatus comprising: a fixing unit configured to thermally fix the toner image; and a first temperature detecting unit configured to detect a temperature of internal air of the apparatus main body housing the image forming unit and the fixing unit; Humidity detection means for detecting the humidity of the internal air, second temperature detection means for detecting the temperature of the dust-proof member of the exposure apparatus, and air blowing means for blowing air toward the recording medium after passing through the fixing means, In each detection result of the air path through which the air after being blown onto the recording medium enters the inside of the apparatus main body, the first temperature detection means, the second temperature detection means, and the humidity detection means And control means for controlling the air volume of the blower means Hazuki, characterized by having a.

  According to the image forming apparatus of the present invention, it is possible to prevent the occurrence of condensation and form a stable image.

Schematic configuration diagram of an image forming apparatus in an embodiment Control block diagram of image forming apparatus Control block diagram of image forming unit Explanatory diagram of air movement (A) is a graph showing the transition of the temperature Tg of the dustproof member with respect to the number of sheets passed when the moisture absorbent paper is passed, and the transition of the dew point temperature Td of the air around the laser scanner, and (b) is a main body with respect to the use environment. A graph showing the transition of the temperature Tg of the dust-proof member and the transition of the dew point temperature Td around the laser scanner with respect to the number of sheets passing at a low temperature Explanatory drawing of the movement of the air inside the machine when the air volume of the cooling fan is reduced Flow chart of control in embodiment 1 Example of table used for fan control An example of an environmental table used for temperature control of the fixing unit when the range of condensation easily is determined in consideration of the target temperature control temperature for each environment Flow chart of control in embodiment 2

Example 1
FIG. 1 is a schematic cross-sectional view of an image forming system according to the present embodiment, and is roughly classified into an image reading apparatus 200 and an electrophotographic system for forming (printing) an image on a sheet (hereinafter referred to as a sheet) S as a recording medium. The image forming apparatus 100 is provided. The image reading apparatus 200 is mounted on the upper part of the image forming apparatus 100, and includes an image reading unit 210 and a document feeding unit 220 that feeds the document D to the image reading unit 210.

  Inside the apparatus main body 100A of the image forming apparatus 100, there are a sheet feeding unit 10, an image forming unit (image forming unit) 20, a fixing unit (fixing unit) 30, and a sheet discharging unit 40 in order from the bottom to the top. Is provided. In the drawing, a paper refeeding unit 50 is provided on the right side of the image forming unit 20 and the fixing unit 30.

  The paper feeding unit 10 feeds the paper S stacked on the feeding cassette 11 or the manual feed tray (multi-feed tray) 17 to the image forming unit 20. The paper S stored in the feeding cassette 11 is fed to the separation roller pair 13 as the pickup roller 12 rotates. When the paper S is being double-fed, it is separated into one sheet by a separation 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 paper S is fed from the manual feed tray 17, the paper S 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 is conveyed to the registration roller pair 16 so that the skew of the sheet S is corrected. Then, the skewed sheet S is conveyed to the image forming unit 20 by the registration roller pair 16 that rotates at a predetermined timing.

  In the image forming unit 20, the surface of a rotating photosensitive drum (hereinafter referred to as drum) 21 as an image carrier is uniformly charged by a charging roller 22. A laser beam corresponding to image information is irradiated to the drum 21 (scanning exposure) from a laser scanner (laser unit) 23 as an exposure device. Then, the charge charged by the charging roller 22 is removed from the portion of the drum 21 irradiated with the laser light, and an electrostatic latent image corresponding to the image information is formed on the drum surface. A developer (toner) is attached to the electrostatic latent image formed here by the developing roller 24 of the developing device 24A, and is visualized as a developer image (toner image).

  The developer image is conveyed to the transfer nip portion N1 by the rotation of the 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 drum 21 and the transfer roller 25 in the transfer nip portion N1. At this time, the developer image formed on the drum 21 by the bias voltage application from the transfer roller 25 is transferred onto the paper S. The laser light emitted from the laser scanner 23 is controlled based on image data transmitted from the image reading apparatus 200 or the host PC 1 to the CPU 101 (FIG. 2) as a control unit.

  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 33 (FIG. 3) such as a halogen lamp, a fixing roller 31 as a fixing member, a pressure roller 32, and the like. The fixing roller 31 is made of a material such as aluminum and is heated to a predetermined temperature by a heat source 33. 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 between the fixing roller 31 and the pressure roller 32. At this time, the developer image is fixed (heat-fixed) on the paper S by being heated and pressurized. The sheet S on which the developer image is fixed by the fixing unit 30 is conveyed to the discharge unit 40 and discharged to the discharge tray 42 by the discharge roller pair 41.

  The fixing unit 30 is not limited to a heating roller type fixing device that heats the sheet S with the fixing roller 31 as described above. For example, an on-demand fixing system that forms a fixing nip portion N2 by pressing a heat source such as a ceramic heater through an endless film through an endless film, and heats and presses the sheet S while nipping and conveying the sheet S at the nip portion N2. Alternatively, a fixing device or the like may be used.

  When images are formed on both sides of the sheet S, the discharge roller before the rear end of the sheet S passes through the discharge roller pair 41 when the sheet S on which the image is formed on the first side is conveyed by the discharge roller pair 41. The pair 41 is temporarily stopped. Further, by rotating the discharge roller pair 41 in the reverse direction, the sheet S is reversed and conveyed to the sheet refeeding unit 50.

  The sheet S transported to the refeed unit 50 is transported along a refeed path PS2 indicated by a broken line by refeed roller pairs 51a and 51b, and is transported to a registration roller pair 16 by a refeed roller pair 51c. Then, after the skew is corrected by the registration roller pair 16, the sheet S in an inverted state is conveyed to the transfer nip portion N <b> 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 surface of the sheet S, and the sheet S on which the image is formed on both sides is discharged by the discharge roller pair 41. It is discharged to the discharge tray 42.

  In addition, an environmental sensor S1 is installed in the image forming apparatus 100 as an environmental condition detection unit that detects the temperature and humidity around the laser scanner 23. This environmental sensor S1 is installed in the same space that is not shielded from the laser scanner 23, and can detect the temperature and humidity around the laser scanner. That is, the environment sensor S1 can detect the temperature and humidity of the internal air of the apparatus main body 100A housing the image forming unit 20 and the fixing unit 30 as electrical signals.

  A thermistor (first temperature detection means) is generally known as the temperature detection means, and a capacitance sensor (humidity detection means) is generally known as the humidity detection means. In the present embodiment, they are combined. A composite sensor is provided as an environmental sensor S1.

  In addition, a dustproof member 23a, which is a transparent member (a translucent member that transmits light), is installed in the laser emission portion of the laser scanner 23. A dust-proof member temperature detection means (second temperature detection means for detecting the surface temperature of the dust-proof member 23a) 23b for detecting the temperature around the dust-proof member 23a is provided. In this embodiment, the temperature detecting means 23b is a thermistor.

  FIG. 2 is a control block diagram of the image forming system of FIG. Reference numeral 101 denotes a CPU as 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 is connected to the image reading device control unit 120 that controls the document reading operation and the document conveying operation by the image reading device 200, the image reading device control unit 120, or the image signal processing unit 110 that processes the image signal from the host PC 1. Is done. In addition, the CPU 101 performs an image forming apparatus control unit 130 that forms an image on the paper S in accordance with an image signal sent from the image signal processing unit 110, performs setting of the main body, and other operations and displays for displaying a message to the user. Connected to the unit 140.

FIG. 3 is a block diagram of the image forming apparatus control unit 130 in FIG. The dew point temperature of the internal air of the apparatus main body 100A is calculated based on the temperature Ts and humidity Hs around the laser scanner 23 detected by the environmental sensor S1 by the CPU 121 in FIG. Yes. Specifically, the dew point temperature Td is calculated by calculating the saturated water vapor pressure ew from the SON-NTAG equation, and calculating the water vapor pressure e at the temperature Ts around the laser scanner 23 as follows: e = H / 100 × ew
Ask for.

And dew point temperature Td is set to y = ln (e / 611.213)
If y ≧ 0,
Td = 13.715y + 8.4262 × 10 ⁻¹ y ² + 1.90848 × 10 ⁻² y ³ + 7.8158 × 10 ⁻³ y ⁴
If y <0,
Td = 13.7204y + 7.336631 × 10 ⁻¹ y ² + 3.332136 × 10 ⁻² y ³ + 7.78559 × 10 ⁻⁴ y ⁴
Calculated by

  In FIG. 3, the image forming apparatus control unit 130 includes a CPU 121 as a control unit. Similar to the control block diagram of the image forming system in FIG. 2, the CPU 121 includes a RAM 122 used as storage of input data, a working storage area, and the like, and a ROM 123 that stores programs such as control procedures.

  A voltage control unit U <b> 1 for applying a voltage to the charging roller 22, the developing roller 24, the transfer roller 25, and the heat source 33 is connected to the CPU 121 via the I / O port 124. Further, a laser scanner 23 for exposing the surface of the drum 21 in FIG. 1, a common drive motor driver D1, and a fan motor driver D2 are connected to the CPU 121 via an I / O port 124.

  The common drive motor driver D1 controls the operation of the common drive motor M1 as a drive source for rotating the 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 unit 60 that cools the fixing unit 30 and the sheet S in FIG. The cooling fan 60 is a blowing unit that blows air toward the paper S after passing through the fixing unit 30. An environmental sensor S1 is connected to the CPU 121, and the temperature and humidity in the image forming apparatus can be detected.

  FIG. 4 is a view for explaining the air flow (air path) in the apparatus (inside the apparatus main body) when the image forming apparatus 100 in FIG. An arrow A indicates an air flow (wind path). When printing the moisture-absorbing paper S, the cooling fan 60 always cools the outside air to a constant air volume (in order to cool the paper S heated and pressurized in the fixing unit 30 and the fixing unit 30. The fixing unit 30 and the paper S are sprayed with a predetermined first air volume). 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 as an exposure device inside the image forming apparatus behind the fixing unit 30 due to the airflow generated by the cooling fan 60, condensation may occur in the laser scanner 23. That is, when the air blown by the cooling fan 60 toward the paper S after passing through the fixing unit 30 reaches the laser scanner 23 by the air path A entering the inside of the apparatus main body 100A, condensation occurs in the laser scanner 23. There is a case.

  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 light source of the laser scanner 23 to the drum 21 decreases when condensation occurs on the surface of the dust-proof member 23a installed on the optical path to the drum 21.

  FIG. 5A shows the main body of the apparatus calculated from the transition of the temperature Tg of the dust-proof member 23a with respect to the number of sheets to which the moisture-absorbed sheet S is passed and the temperature and humidity of the space around the laser scanner 23 at that time. The transition of the dew point temperature Td of the internal air.

  The temperature Tg of the dust-proof member 23a indicated by a solid line increases almost linearly as the number of continuous sheets increases (up to about 1 ° C./100 sheets up to 300 sheets, After 300 sheets, the rise in temperature Tg of the dustproof member 23a tends to be saturated). Before passing the paper, the inside of the apparatus main body and the apparatus installation environment are substantially the same temperature. However, when a large amount of moisture-absorbed paper S is passed, the temperature and humidity inside the apparatus main body rises rapidly, so that the temperature and humidity around the laser scanner 23 are increased. The dew point temperature Td indicated by the broken line calculated from the above increases rapidly.

  The temperature Tg of the dust-proof member 23a that gradually rises in accordance with the number of sheets to be passed is a dew point temperature Td that rises when several dozen sheets of moisture-absorbed paper S are passed, depending on the installation environment and conditions of the apparatus. On the other hand, if the predetermined high temperature state cannot be ensured, the dustproof member 23a is condensed. That is, if the difference (Tg−Td), which is the difference between the dew point temperature Td and the temperature Tg of the dustproof member 23a, cannot be equal to or higher than the predetermined first threshold temperature A (1 ° C or higher in this embodiment), the dustproof member 23a Condensation. In this embodiment, this dew condensation case is referred to as dew condensation when the absorbent paper is passed (condensation case due to moisture absorption of the recording medium).

  FIG. 6 shows the flow of air inside the apparatus main body in the image forming apparatus 100 during the execution of the dew condensation countermeasure mode when the dew condensation case determination described later according to the present embodiment determines that dew condensation occurs when the absorbent paper is passed. FIG. Arrow B indicates the flow of air (wind path).

  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 the present embodiment, the output is adjusted to the half speed drive (50%: a predetermined second air volume reduced from the first air volume) with respect to the full speed drive (100%: predetermined first air volume). .

  FIG. 5B shows the transition of the temperature Tg of the dustproof member 23a with respect to the number of sheets passing when the image forming apparatus 100 moved from the low temperature environment is used in a warm environment, and the temperature and humidity of the space around the laser scanner 23 at that time. It is a transition of the dew point temperature Td of the internal air of the apparatus main body calculated from

  The temperature of the dust-proof member 23a indicated by the solid line increases almost linearly as the number of continuous sheets increases (up to about 1 ° C / 100 sheets up to 300 sheets, 300 After the sheet, the rise in the temperature Tg of the dustproof member 23a tends to be saturated). The temperature inside the apparatus main body is low before the paper S is passed. For this reason, when air in a warm environment enters the apparatus main body, there is a possibility that the dust-proof member 23a is condensed before paper is passed.

  In other words, the difference (Tg−Td) between the dew point temperature Td indicated by the broken line calculated from the temperature and humidity around the laser scanner 23 and the temperature Tg of the dustproof member 23a is lower than the predetermined first threshold temperature A1. Then (in this embodiment, less than 1 ° C.), the dustproof member 23a is condensed. In this case, since the condensation has occurred before the sheet is passed, image defects such as a serious decrease in the density of the output image may occur from the first sheet. In this embodiment, this condensation case is referred to as main body low temperature condensation.

  As countermeasures against condensation at a low temperature of the main body, one of the following condensation countermeasure modes (1) to (3) is executed at the time of execution of the pre-image processing operation including the start-up processing of the fixing unit 30, or either Execution of two combinations or all three executions.

(1) Condensation countermeasure mode in which driving of the cooling fan 60 is stopped or changed to a predetermined second air volume U2 (half speed driving) reduced from a predetermined first air volume U1 (full speed driving). Condensation countermeasure mode for extending the image preprocessing operation (3) Condensation countermeasure for changing the fixing temperature adjustment temperature of the fixing unit 30 to a predetermined second fixing temperature adjustment temperature T2 higher than the predetermined first fixing temperature adjustment temperature T1. mode.

  Here, the start-up process of the fixing unit 30 is a warm-up process that drives the fixing unit 30 and supplies power to the heat source 33 to raise the fixing member to a predetermined target temperature. The pre-image forming processing operation is executed when the apparatus power is turned on (when the power is turned on) or when waiting for the apparatus to return from the standby state (sleep state). Up processing (so-called pre-multi-rotation operation or pre-rotation operation: initial operation).

  As a result of the execution of the dew condensation countermeasure mode, the temperature of the internal air of the apparatus body rises, the temperature of the dustproof member 23a also rises, and the condensation is recovered by raising the temperature of the dustproof member 23a above the dew point temperature Td. Yes.

  In the present embodiment, the transition of the dew point temperature Td in the space around the laser scanner 23 inside the apparatus main body and the temperature Tg of the dustproof member 23a at that time is monitored, and the dewpoint temperature Td and the temperature Tg of the dustproof member 23a are recovered. Condensation is recovered by extending the pre-processing operation until image formation. This prevents a decrease in image density due to condensation on the dustproof member 23a. Further, the temperature adjustment temperature is set to 20 ° C. higher than the normal temperature adjustment temperature (first fixing temperature adjustment temperature T1) of the fixing unit 30 (second fixing temperature adjustment temperature T2), and the cooling fan 60 is set to half speed. It is operated (second air volume). That is, all three anti-condensation modes (1) to (3) are executed.

  Based on the flowchart of FIG. 7, a method for separating a condensation case in this embodiment and a countermeasure for condensation after the separation will be described. 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 1 in FIG. 1 to the CPU 101 in FIG. 2 in the standby state (sleep state) of the image forming apparatus 100, an image forming pre-processing operation including a start-up process of the fixing unit 30 (previous Rotation operation) is executed. The CPU 121 in FIG. 3 rotates the common drive motor via the common drive motor driver D1 in FIG. At the same time, a voltage is applied to the heat source 33 in FIG. 3 via the voltage control unit U1 in FIG. Thereby, the fixing unit 30 is started up (step S701).

  At the start of this image forming pre-processing operation, the temperature and humidity around the laser scanner 23 are detected by the environmental sensor S1 in FIG. 3, and the temperature of the dustproof member 23a is detected by the thermistor 23b (step S702). The dew point temperature Td is calculated based on the environmental conditions of the temperature and humidity around the laser scanner 23 detected in step S702 (step S703). The calculated dew point temperature Td is compared with the temperature Tg of the dust-proof member 23a detected by the thermistor 23b (step S704).

  In the dew condensation case determination 1 in step S705, it is determined whether or not the main body has dew condensation from the difference (Tg−Td) between the dew point temperature Td and the temperature Tg of the dustproof member 23a. That is, when (Tg−Td) is equal to or higher than the value of the first threshold temperature A1, it is determined that there is no condensation when the main body is at a low temperature. In this embodiment, the first threshold temperature A1 is set to 1 ° C. Therefore, when (Tg−Td) ≧ 1 ° C., it is determined that there is no condensation at low temperature of the main body.

  Then, the fan motor M2 in FIG. 3 is controlled via the fan motor driver D2 in FIG. In this embodiment, the cooling fan 60 shown in FIG. 6 is driven at full speed (first air volume U1) (step S706), and a printing operation (image forming operation) is executed (implemented) (step S707).

  Next, the transition of the dew point temperature Td during paper feeding (while the recording medium is being fed during the image forming operation) is confirmed (step S708). In the dew condensation case determination 2 in step S709, the rate of change b = (Td′−Td) / the number of output sheets of the dew point temperature Td ′ for each predetermined number of sheets being passed is compared with a predetermined change rate threshold B. When the rate of change b is smaller than the rate of change threshold B, it is possible to ensure that the temperature of the dust-proof member 23a is higher than the value of the first threshold temperature A1 (1 ° C.) with respect to the dew point temperature Td.

  In this embodiment, the change rate threshold B is set to 0.1. When the rate of change in dew point temperature Td for every 10 sheets passed (Td′−Td) / number of output sheets <0.1, the temperature of the dustproof member 23a is higher by 1 ° C. or more than the dew point temperature Td. It can be secured. This eliminates the possibility of condensation. Therefore, the fan 60 maintains full speed driving (step S710) and continues the printing operation (step S711).

  When the print job is finished (step S712), the fixing unit operation is stopped (step S713), the fan operation is stopped (step S714), and the process is finished. If the print job is not completed, the process returns to the dew condensation case determination 1 (step S705).

  Next, when the dew point temperature Td change rate (Td′−Td) / number of output sheets ≧ 0.1 in the dew condensation case determination 2 in step S709, the temperature of the dustproof member 23a is 1 ° C. with respect to the dew point temperature Td. A higher state cannot be secured. Therefore, it is determined that there is a risk of condensation when the absorbent paper is passed. Then, the fan motor M2 shown in FIG. 3 is controlled via the fan motor driver D2 shown in FIG. That is, half-speed driving (second air volume U2) of the fan 60 of FIG. 6 is executed (step S715), and the printing operation is continued (step S716).

  If the print job is finished (step S717), the fixing unit operation is stopped (step S718), the fan operation is stopped (step S719), and the process is finished. If the print job is not completed, the printing operation is executed in the moisture absorption paper passing condensation prevention mode (step S715) (step S716). When the print job is finished (step S717), the fixing unit operation is stopped (step S713), and the fan operation is stopped (step S714), and the process is finished. If the print job is not completed, the process returns to the moisture absorption paper dew condensation countermeasure mode (step S715) and the printing operation (step S716) is continued.

  If it is determined in the dew condensation case determination 2 in step S709 that the dew condensation is caused when the moisture absorbent paper is passed, the dew case is condensed on the display unit of the operation / display unit 140 (FIG. 2) as a notification unit. Can be displayed to prompt the user to replace the paper. This sequence can be performed instead of steps S715 to S717 or simultaneously with the execution of these steps.

  If (Tg−Td) ≧ 1 ° C. is not satisfied in the dew condensation case determination 1 in step S705, it is determined that the main body resistance is dew condensation. Then, a dew condensation alarm indicating that the dew condensation case is the dew condensation case of the main body resistance dew condensation is notified to the display unit of the operation / display unit 140 (FIG. 2) which is a notification unit, and the user is made aware of this (step S718). .

  As the condensation recovery operation in the main body low-temperature condensation mode, the fan half-speed operation (second air volume U2) and the fixing temperature adjustment temperature are increased by 20 ° C. from the normal (first fixing temperature adjustment temperature T1) (second adjustment). The fixing temperature adjustment temperature T2) and the pre-rotation operation are extended (step S719).

  In this dew condensation recovery operation process, the transition of the dew point temperature Td and the temperature Tg of the dustproof member 23a is confirmed (step S720). And it is confirmed whether (Tg-Td) became more than the value of 2nd threshold temperature A2 higher than 1st threshold temperature A1 (step S721). In this embodiment, the second threshold temperature A2 is set to 2 ° C. Accordingly, if (Tg−Td) ≧ 2 ° C. in the dew condensation recovery confirmation in step S721, the dew condensation at the low temperature of the main body is improved and it is determined that the print is possible. Then, the condensation alarm is canceled (step S722), the fan is driven at full speed (step S723), and the printing operation is executed (step S724).

  That is, when (Tg−Td) becomes equal to or higher than the second threshold temperature A2 higher than the first threshold temperature A1 during execution of the dew condensation countermeasure mode for the main body low temperature condensation, the pre-imaging processing operation is performed. Then, the image forming apparatus is allowed to perform an image forming operation.

  When the print job is finished (step S725), the fixing unit operation is stopped (step S713), and the fan operation is stopped (step S714), and the process is finished. If the print job is not completed, the fan is driven at full speed (step S723), and the print operation is executed (step S724).

  If (Tg−Td) <2 ° C. in the dew condensation recovery confirmation in step S721, it is determined that the main body low temperature dew condensation is insufficiently improved, and the process returns to step S719 to execute the dew condensation recovery operation.

  In order to cool the sheet S after being heated and pressurized in the fixing unit 30 in FIG. 6 and the fixing unit 30 in FIG. 6, it is desirable to always drive the cooling fan 60 in FIG. However, in some cases where condensation occurs, the cooling fan 60 is driven at half speed in order to avoid the occurrence of condensation, thereby preventing the condensation 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 paper S can be maintained.

  In this embodiment, the change rate b of dew point temperature Td = (Td′−Td) / the number of output sheets is output every 10 sheets. It is also possible to change the number of output sheets.

  In this embodiment, the cooling fan 60 is controlled in two stages of full speed driving and half speed driving. However, the cooling fan 60 can be further divided and controlled.

  In this embodiment, the dew condensation case determinations 1 and 2, the temperature at the time of dew condensation confirmation determination, the dew point temperature change rate, and the fixing temperature control are values that can be set as appropriate depending on the internal structure of each apparatus main body.

  In this embodiment, the fan control, the fixing temperature adjustment control, and the pre-rotation operation time are changed as the dew condensation recovery operation. However, if any control is performed, the dew condensation can be expected.

  As described above, in the image forming apparatus of the present embodiment, the dew point is determined by directly detecting the dew point temperature around the laser scanner 23 and the temperature of the dustproof member 23a to be dewed, and the dew case is determined. Perform condensation avoidance operation and condensation recovery operation. Therefore, even if moisture absorbent paper is used, the air humidified in the fixing unit 30 does not reach the laser scanner 23. Further, the condensation at the low temperature of the main body can be eliminated with the minimum necessary recovery operation until the condensation is recovered. Therefore, it is possible to prevent image defects due to condensation of the laser scanner as the exposure apparatus.

Example 2
In the image forming apparatus 100 described in the first embodiment, a case where the setting temperature of the fixing temperature adjustment is switched depending on the environment will be described.

  If the target temperature control temperature for fixing is the same in all environments, it is possible to divide the area where condensation is likely to occur in the environmental table shown in FIG. 8. The amount of heat required for fixing varies as the environment goes, and the target temperature control temperature increases. When the target temperature adjustment temperature for fixing increases, the amount of water vapor generated from the paper S also increases. Therefore, control is performed with an environment table for target temperature control in consideration of the influence of water vapor generated from the paper S in addition to the temperature and humidity of the environment. Is required. FIG. 9 is an example of an environment table used for temperature control of the fixing unit 30 in the case where the environment is divided in consideration of the target temperature adjustment temperature required for fixing depending on the environment.

  In the area C, the target temperature adjustment temperature for fixing is as low as 150 ° C. in a high-temperature and high-humidity environment, and it is difficult for condensation to occur because the amount of water vapor generated is small because condensation is unlikely to occur and the target temperature adjustment temperature for fixing is low. Consider the case of dew point temperature Td change rate (Td′−Td) / number of output sheets ≧ 0.1 (step S709) in the dew condensation case determination 2 of Example 1 (condensation when passing through moisture-absorbing paper). In this case, if the control is performed at 145 ° C. (third fixing temperature adjustment temperature T3) that is −5 ° C. lower than the normal target temperature adjustment temperature (first fixing temperature adjustment temperature T1), condensation can be prevented more reliably. it can.

  In the region A, since the target temperature adjustment temperature for fixing is as high as 190 ° C. in order to satisfy the fixing property in a low temperature environment, and the amount of water vapor generated from the paper S is large, condensation is likely to occur. Consider a case where it is determined that condensation occurs when the absorbent paper of Example 1 is passed. In this case, the curling of the paper S is less likely to occur compared to the high temperature and high humidity environment. Therefore, if the cooling fan 60 is stopped or rotated at the necessary minimum speed and the temperature is lowered by −20 ° C. from the normal target temperature control temperature. Further, curling and condensation can be prevented more reliably.

  Region B is an environment between regions A and C. Since the target temperature adjustment temperature for fixing is 180 ° C., when it is determined that condensation occurs when the moisture absorbent paper is passed in the first embodiment, the cooling fan 60 is slowed down so that the target temperature adjustment temperature for fixing is less than the normal target temperature adjustment temperature. By lowering the temperature by 10 ° C., it becomes possible to more reliably prevent curling and condensation.

  Note that this environment table can be divided into regions according to the likelihood of condensation, and if the temperature is adjusted to a target temperature that achieves both condensation, curl, and fixability for each region, it is limited to the above conditions. It is not a thing.

  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. The processing in FIG. 10 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 1 in FIG. 1 to the image forming apparatus 100, the CPU 121 in FIG. 3 detects the temperature and humidity around the laser scanner 23 by the environment sensor S1 in FIG. 3 (step S1001). . Next, environment determination is performed (step S1002), and the environmental conditions of temperature and humidity detected in step S1001 are collated with the table of FIG. 9 (step S1003).

  Next, when the environmental condition is in the region B from the comparison result of temperature and humidity, the CPU 121 in FIG. 3 rotates the common drive motor via the common drive motor driver D1 in FIG. At the same time, a voltage corresponding to the environmental conditions of the temperature and humidity detected in step S1001 is applied to the heat source 33 of FIG. 3 via the voltage control unit U1 of FIG. Accordingly, the start-up process is performed so that the fixing unit 30 is driven and the target temperature control temperature (for example, 180 ° C.) is reached (step S1003).

  Next, the dew point temperature Td is calculated based on the environmental conditions of the temperature and humidity around the laser scanner 23 detected in step S1001 (step S1004). Next, the temperature Tg of the dustproof member 23a is acquired by the thermistor 23b (step S1005), and the calculated dew point temperature Td is compared with the surface temperature Tg of the dustproof member 23a (step S1006).

  Next, in dew condensation case determination 1 in step S1007, it is determined from (Tg−Td) whether the main body is dew condensation at low temperature. When (Tg−Td) ≧ 1 ° C., it is determined that there is no condensation at a low temperature of the main body, and the fan motor M2 in FIG. 3 is controlled via the fan motor driver D2 in FIG. Here, the cooling fan 60 of FIG. 6 is driven at full speed (step S1007), and the printing operation is executed (step S1009).

  Next, the transition of the dew point temperature Td during paper feeding is confirmed (step S1010). In the dew condensation case determination 2 in step S1011, when the rate of change of the dew point temperature Td for every 10 sheets passed (Td′−Td) / number of output sheets <0.1, the temperature of the dustproof member 23a with respect to the dew point temperature Td. Can be assured to be higher by 1 ° C. or more. That is, there is no possibility of condensation.

  Therefore, the fan 60 maintains full speed driving (step S1012) and continues the printing operation (step S1013). When the print job is finished (step S1014), the fixing unit operation is stopped (step S1015), and the fan operation is stopped (step S1016), and the process is finished. If the print job is not finished, the process returns to the dew condensation case determination 1 in step S1007.

  Next, when the dew point temperature Td change rate (Td′−Td) / number of output sheets ≧ 0.1 in the dew condensation case determination 2 in step S1011, the temperature of the dustproof member 23a of the laser scanner 23 with respect to the dew point temperature Td. However, it is not possible to secure a state of higher than 1 ° C. Therefore, it is determined that there is a risk of condensation when the absorbent paper is passed, and the fan motor M2 of FIG. 3 is controlled via the fan motor driver D2 of FIG. 60 half-speed driving is executed (step S1017).

  Furthermore, when the environmental condition determined from the temperature / humidity comparison result in step S1002 is in region B, the CPU 121 in FIG. 3 rotates the common drive motor via the common drive motor driver D1 in FIG. At the same time, a voltage corresponding to the environmental conditions of the temperature and humidity detected in step S1001 is applied to the heat source 33 of FIG. 3 via the voltage control unit U1 of FIG. As a result, the fixing unit 30 is driven and heated (temperature rise, temperature adjustment) so as to be the target temperature adjustment temperature (for example, in the case of region B, the normal temperature adjustment temperature is 180 ° C.-10 ° C. 170 ° C.) (step S1018 ) And the printing operation is continued (step S1019).

  When the print job is finished (step S1020), the fixing unit operation is stopped (step S1015), and the fan operation is stopped (step S1016), and the process is finished. If the print job is not completed, heating is performed so as to reach a target temperature adjustment temperature (for example, in the case of region B, the normal temperature adjustment temperature is 180 ° C.-10 ° C. 170 ° C.) in the moisture absorption paper passing condensation prevention mode (step S1017). This is performed (step S1018). Then, a printing operation is executed (step S1019).

  If (Tg−Td) ≧ 1 ° C. is not satisfied in the dew condensation case determination 1 in step S1007, it is determined that the main body is dew condensation at a low temperature, and a dew condensation alarm is notified (step S1021). As the dew condensation recovery operation in the dew condensation mode at the time of low temperature of the main body, the fan half speed operation, the fixing temperature adjustment is increased by 20 ° C. than normal, and the pre-rotation is extended (step S1022). The dew point temperature Td and the temperature Tg of the dustproof member 23a The transition is confirmed (step S1023).

  If (Tg−Td) ≧ 2 ° C. in the dew condensation recovery confirmation in step S1024, it is determined that dew condensation has improved and the print is ready, and the dew condensation alarm is canceled (step S1025). Then, the fan 60 is driven at full speed (step S1026), and a printing operation is executed (step S1027). When the print job is finished (step S1028), the fixing unit operation is stopped (step S1015), and the fan operation is stopped (step S1016), and the process is finished.

  If the print job is not finished, the fan is driven at full speed (step S1026), and the print operation is executed (step S1027). If Tg−Td <2 ° C. in the dew condensation confirmation in step S1024, it is determined that the dew condensation is insufficiently improved, and the process returns to (step S1022) to execute the dew condensation recovery operation.

  As described above, in order to cool the sheet S after being heated and pressurized in the fixing unit 30 in FIG. 6 and the fixing unit 30 in FIG. 6, the cooling fan 60 in FIG. 6 is always driven at full speed. It is desirable. However, in environmental conditions where condensation is likely to occur, the wind speed of the cooling fan 60 is reduced to prevent condensation in the laser scanner 23 of FIG.

  In consideration of the target temperature control temperature required for fixing by the environment, the condensation tends to occur as the temperature goes from a high temperature and high humidity environment to a low temperature environment as shown in the table of FIG. Therefore, even if the wind speed of the cooling fan 60 is reduced as the environment goes to a lower temperature side, the air volume necessary for cooling the fixing unit 30 and the paper S can be maintained.

  Further, when it is determined in the dew condensation case determination 2 in step S1011 that the dew condensation occurs when the moisture absorbent paper is passed, the target temperature adjustment temperature is lowered below the normal temperature according to the environment table in FIG. -10 ° C 170 ° C). Thereby, even when moisture-absorbing paper is passed, it is possible to reliably prevent the occurrence of condensation in the laser scanner 23 of FIG.

  In this embodiment, the change rate b of dew point temperature Td = (Td′−Td) / the number of output sheets is output every 10 sheets. It is also possible to change the number of output sheets.

  In this embodiment, the cooling fan 60 is controlled in two stages of full speed driving and half speed driving. However, the cooling fan 60 can be further divided and controlled.

  In this embodiment, the dew condensation case determinations 1 and 2, the temperature at the time of dew condensation confirmation determination, the dew point temperature change rate, and the fixing temperature control are values that can be set as appropriate depending on the internal structure of each apparatus main body. In this embodiment, the fan control, the fixing temperature adjustment control, and the pre-rotation time are changed as the dew condensation recovery operation. However, if any control is performed, the recovery of the dew condensation can be expected.

  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.

  As described above, in the image forming apparatus of the present embodiment, the dew point is determined by directly detecting the dew point temperature around the laser scanner 23 and the temperature of the dustproof member 23a to be dewed, and the dew case is determined. Perform condensation avoidance operation and condensation recovery operation. Therefore, even if moisture absorbent paper is used, the air humidified in the fixing unit 30 does not reach the laser scanner 23. Further, the condensation at the low temperature of the main body can be eliminated with the minimum necessary recovery operation until the condensation is recovered. Therefore, it is possible to prevent image defects due to condensation of the laser scanner as the exposure apparatus.

  In the image forming apparatus according to the present embodiment, the temperature condition of the fixing unit is related to the curling / fixing property when using moisture absorbing paper, an environmental condition in which condensation easily occurs based on the environmental condition. Set the value within a range that does not break down. By doing so, generation of water vapor generated in the fixing unit 30 can be suppressed, and humidified air 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.

《Other matters》
(1) In the control flow of FIGS. 7 and 10, the dew case determination 1 is performed during the pre-rotation operation when the image forming apparatus 100 returns from the sleep state, but when the apparatus power is turned on (after the jam processing) It may also be executed during multi-rotation operation (including when the power is turned on).

  (2) In addition to a device that fixes an unfixed toner image as a fixed image, the fixing unit 30 improves the glossiness by heating and pressurizing a toner image that has been presupposed to the paper or once heated and fixed. The case of an image quality reforming device (referred to as this fixing device) is also included.

  (5) In the image forming apparatus, the image forming unit for forming the toner image on the paper is not limited to the transfer type electrophotographic image forming unit of the embodiment. For example, an electrophotographic image forming unit that uses a photosensitive paper as a paper and forms a toner image directly on the photosensitive paper may be used. Further, it may be a transfer type electrostatic recording image forming unit or a magnetic recording image forming unit using an electrostatic recording dielectric or a magnetic recording magnetic material as an image carrier. Further, an electrostatic recording image forming unit or a magnetic recording image forming unit may be used in which electrostatic recording paper or magnetic recording paper is used as the paper and a toner image is directly formed thereon. A mono-color image forming unit may be used.

  DESCRIPTION OF SYMBOLS 100..Image forming apparatus, 100A..Main body, S..Recording medium, 20..Image forming unit, 30..Fixing unit, 23..Exposure device, S1..Environmental sensor (first temperature detecting means And humidity detecting means), 23a ... dust-proof member, 23b ... humidity detecting means, 60 ... air blowing means, 130 ... control means

Claims (14)

An image forming apparatus comprising: an image forming unit having an exposure device that forms a toner image on a recording medium; and a fixing unit that thermally fixes the toner image formed on the recording medium by the image forming unit.
First temperature detecting means for detecting the temperature of the internal air of the apparatus main body containing the image forming means and the fixing means;
Humidity detecting means for detecting the humidity of the internal air;
Second temperature detecting means for detecting the temperature of the dust-proof member of the exposure apparatus;
An air blowing means for blowing air toward the recording medium after passing through the fixing means;
An air path through which air after being blown onto the recording medium enters the inside of the apparatus main body;
An image forming apparatus comprising: a control unit that controls an air volume of the blowing unit based on detection results of the first temperature detection unit, the second temperature detection unit, and the humidity detection unit. .   The image forming means has a charged image carrier, the exposure device is a device for exposing the charged image carrier based on image data, and the dust-proof member is supplied from a light source of the exposure device. The image forming apparatus according to claim 1, wherein the image forming apparatus is installed on an optical path of light toward the body.   The image forming apparatus according to claim 2, wherein the dustproof member is a translucent member that transmits the light.   The control unit is configured to perform a dew point temperature Td of the internal air obtained based on detection results of the first temperature detection unit and the humidity detection unit during execution of a pre-image forming processing operation including a start-up process of the fixing unit. And the difference between the temperature Tg of the dust-proof member detected by the second temperature detecting means (Tg−Td) is lower than a predetermined first threshold temperature A1, the driving of the air blowing means is stopped. 4. The dew condensation countermeasure mode is executed, wherein the air volume of the air blowing means is set to a predetermined second air volume U2 that is lower than the predetermined first air volume U1. The image forming apparatus described in 1.   The control unit is configured to perform a dew point temperature Td of the internal air obtained based on detection results of the first temperature detection unit and the humidity detection unit during execution of a pre-image forming processing operation including a start-up process of the fixing unit. And (Tg−Td), which is a difference between the temperature Tg of the dust-proof member detected by the second temperature detecting means and lower than a predetermined first threshold temperature A1, the image pre-processing operation is performed. The image forming apparatus according to claim 1, wherein an anti-condensation countermeasure mode is executed.   The control unit is configured to perform a dew point temperature Td of the internal air obtained based on detection results of the first temperature detection unit and the humidity detection unit during execution of a pre-image forming processing operation including a start-up process of the fixing unit. And (Tg−Td), which is a difference between the temperature Tg of the dustproof member detected by the second temperature detecting means and lower than a predetermined first threshold temperature A1, the fixing temperature control of the fixing means. 4. The dew condensation countermeasure mode for changing the temperature to a predetermined second fixing temperature adjustment temperature T <b> 2 higher than the predetermined first fixing temperature adjustment temperature T <b> 1 is executed. 5. The image forming apparatus described.   The control unit is configured to perform a dew point temperature Td of the internal air obtained based on detection results of the first temperature detection unit and the humidity detection unit during execution of a pre-image forming processing operation including a start-up process of the fixing unit. And (Tg−Td), which is the difference between the temperature Tg of the dust-proof member detected by the second temperature detecting means and equal to or higher than a predetermined first threshold temperature A1, the fixing temperature of the fixing means. 4. A dew condensation countermeasure mode for changing the temperature adjustment to a predetermined third fixing temperature adjustment temperature T3 lower than a predetermined first fixing temperature adjustment temperature T1 is executed. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 4, wherein the first threshold temperature A1 is 1 ° C.   When the (Tg−Td) becomes equal to or higher than a predetermined second threshold temperature A2 higher than the first threshold temperature A1 during execution of the dew condensation countermeasure mode, the control means The image forming apparatus according to claim 4, wherein the image forming apparatus enables the image forming operation of the image forming apparatus after finishing the processing operation.   The image forming apparatus according to claim 9, wherein the second threshold temperature A2 is 2 ° C.   The control means, at the start of the pre-image processing operation including the start-up processing of the fixing means, the dew point temperature Td of the internal air obtained based on the detection results of the first temperature detection means and the humidity detection means. And (Tg−Td), which is the difference between the temperature Tg of the dust-proof member detected by the second temperature detecting means and equal to or higher than a predetermined first threshold temperature A1, is recorded during the image forming operation. If the rate of change b = (Td′−Td) / output number of dew point temperature Td ′ for every predetermined number of recording media during medium feeding is greater than or equal to a predetermined rate of change threshold B, 4. The image forming apparatus according to claim 1, wherein the air volume is set to a predetermined second air volume U <b> 2 that is lower than a predetermined first air volume U <b> 1. 5.   When the rate of change b = (Td′−Td) / number of output sheets is smaller than a predetermined rate of change threshold B, the control unit performs an image forming operation with the air volume of the blowing unit as the first air volume U1. The image forming apparatus according to claim 11.   Informing means, and the control means informs the dew condensation case occurring in the apparatus main body based on the detection results of the first temperature detecting means, the second temperature detecting means and the humidity detecting means. 12. The image forming apparatus according to claim 1, wherein the image forming apparatus displays the image on a display unit.   The control means, at the start of the pre-image processing operation including the start-up processing of the fixing means, the dew point temperature Td of the internal air obtained based on the detection results of the first temperature detection means and the humidity detection means. And (Tg−Td), which is the difference between the temperature Tg of the dust-proof member detected by the second temperature detecting means and equal to or higher than a predetermined first threshold temperature A1, is recorded during the image forming operation. When the rate of change b = (Td′−Td) / output number of dew point temperature Td ′ per predetermined number of recording media during medium feeding is equal to or greater than a predetermined rate of change threshold B, the main body of the apparatus The image forming apparatus according to claim 13, wherein the image forming apparatus displays the fact that the dew condensation case that has occurred is a dew condensation case due to moisture absorption of the recording medium and prompts the user to replace the recording medium.