JP6598560B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile machine, and a multifunction machine having a plurality of these functions.

  In an electrophotographic image forming apparatus, generally, a recording material (media, sheet: hereinafter referred to as paper) carrying a toner image is nipped and conveyed while being heated and pressed at a nip formed by a heating rotating body and a pressure member. Thus, a fixing device that fixes a toner image onto a sheet is often used.

  In conventional image forming apparatuses, when the fixing temperature adjustment temperature is switched according to the switching of the type of paper to be used, or when the temperature of the heating rotator is lowered by continuous paper passing, image formation is performed until the temperature becomes stable again. There is control that interrupts the operation of the device. This control reduces the total productivity of the image forming apparatus.

  In order to solve such problems, a tandem fixing method has recently been proposed (Patent Document 1). This includes first and second fixing devices, and according to the basis weight and type of paper to be used, a transport path using only the first fixing device and both the first and second fixing devices. The transfer path using the apparatus can be switched.

  If this tandem fixing method is used, the number of times of switching the fixing temperature control temperature of each fixing device can be suppressed, and the time for interrupting the operation of the image forming apparatus can be shortened accordingly. Furthermore, since the amount of heat applied to the paper to be used can be easily switched by providing two fixing devices, the gloss of the toner image can be easily controlled.

JP 2007-199288 A

  When the paper is passed in the morning when the temperature inside the image forming apparatus is low and the temperature inside the apparatus is low, water vapor generated from the paper that has received heat when the paper passes through the fixing device is transported in the paper conveying direction of the fixing device. Condensation may occur on the sheet conveyance guide located downstream and still in a low temperature state. That is, water droplets may adhere on the guide member.

  In the tandem fixing type image forming apparatus described above, when a sheet is passed with water droplets attached to the guide member downstream of the first fixing device, the sheet having the water droplets transferred to the image surface is second fixed. It is fixed by the device. As a result, the transferred portion of the water droplets evaporates in the nip portion of the second fixing device, causing a problem that the surface property of the image surface changes locally and an abnormal image is formed. In order to solve this problem, a method such as providing a heating member for warming the downstream guide member can be considered, but this is not desirable because it leads to complication of the apparatus.

  The present invention has been made in view of the above-described problems. An object of the present invention is to provide an image forming apparatus capable of suppressing the dew condensation on the guide member without complicating the apparatus in the tandem fixing type image forming apparatus.

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 forms a toner image on a recording material, and a heating unit that heats the recording material conveyed from the image forming unit. A first pair of rotators forming a first nip portion; a second pair of rotators forming a second nip portion for heating the recording material conveyed from the first nip portion ; A guide member that receives and guides the recording material discharged from the first nip portion, a conveyance portion that conveys the recording material guided by the guide member to the second nip portion, and the conveyance portion An air flow generating means for generating an air flow toward the second nip portion, and an exhaust that is provided in the vicinity of the first pair of rotating bodies and exhausts the atmosphere around the first pair of rotating bodies to the outside of the apparatus. Acquire information about the temperature of the fan and the guide member When the information indicates that the guide member is at a predetermined temperature or higher when the power of the obtaining unit and the apparatus is turned on, the air flow generating means is turned on during the warming up of the first pair of rotating bodies. And when the information indicates that the guide member is below a predetermined temperature, the air flow generating means is turned on during warming up of the first pair of rotating bodies. And a control unit that controls to turn off the exhaust fan.

  According to the present invention, in the tandem fixing type image forming apparatus, it is possible to suppress dew condensation on the guide member without complicating the apparatus.

It is a control flowchart of the exhaust fan and conveyance path fan in an Example. 1 is a schematic configuration diagram of an image forming apparatus in an embodiment. It is a block diagram of a control system. FIG. 6 is an explanatory diagram of a control sequence of the image forming apparatus. FIG. 3 is a schematic cross-sectional view illustrating a configuration of a first fixing device. It is a cross-sectional schematic diagram which shows the structure of a 2nd fixing device. FIG. 6 is a diagram illustrating an air flow in the vicinity of a first fixing device and a second fixing device when an exhaust fan and a blower fan are in an ON state. FIG. 6 is a diagram illustrating an air flow in the vicinity of a first fixing device and a second fixing device when an exhaust fan and a blower fan are in an OFF state. FIG. 6 is a diagram illustrating a time transition of a surface temperature of a conveyance guide from when an image forming apparatus is turned on until a sheet is passed.

  Embodiments of the present invention will be described below, but this embodiment is an example of the best embodiment of the present invention, but the present invention is not limited to these embodiments.

Example 1
(1) Image Forming Unit FIG. 2 is a longitudinal sectional view of a schematic configuration of the image forming apparatus 1 in the present embodiment. The image forming apparatus 1 is an intermediate transfer type and tandem fixing type full-color electrophotographic printer. That is, it operates based on a print job (print signal) input from the external host device C such as a personal computer to the control unit A to form a full-color toner image or a mono-color toner image on a recording material (hereinafter referred to as paper) P. be able to. B is an operation unit of the image forming apparatus 1. Since the configuration of the image forming apparatus 1 shown in FIG.

  Reference numeral 2 denotes an image forming unit inside the apparatus main body 1A of the image forming apparatus 1. The image forming unit 2 forms a toner image on the paper P. In this embodiment, the image forming unit 2 includes four image forming units U (UY, UM, UC, UK) and an intermediate transfer belt unit 9. Each image forming unit U includes a photosensitive drum 3, a charger 4, a laser scanner 5, a developing device 6, a primary transfer device 7, a drum cleaner 8, and the like. In order to avoid complication of the drawing, the reference numerals for these devices in the image forming units UM, UC, UK other than the image forming unit UY are omitted.

  Each image forming unit U forms yellow (Y), magenta (M), cyan (C), and black (K) toner images on the photosensitive drum 3 that is rotationally driven in a predetermined manner. Then, the toner images of the four colors are sequentially superposed on the intermediate transfer belt (endless belt) 10 that rotates from the photosensitive drum 3 of each image forming unit U, and is primarily transferred. As a result, an unfixed toner image with four colors superimposed is formed on the belt 10.

  Then, the paper P is introduced at a predetermined control timing into the secondary transfer nip portion, which is a pressure contact portion between the belt 10 and the secondary transfer roller 13, and the toner image on the belt 10 is secondary to the paper P. Transcribed. The sheet P is separated and fed from the sheet feeding cassette 11, is introduced into the secondary transfer nip portion through the conveying portion (conveying path) a including the registration roller pair 12, and is nipped and conveyed. In this nipping and conveying process, the four-color superimposed unfixed toner image on the belt 10 is secondarily transferred onto the paper P sequentially. The paper P that has exited the secondary transfer nip portion is sequentially separated from the belt 10 and introduced into the first fixing device 100 in the tandem fixing portion by the conveying portion b.

  Toner and other foreign matters remaining on the belt 10 are removed by the belt cleaner 14. The unfixed toner image Ta (FIG. 5) on the paper (on the recording material) introduced into the first fixing device 100 from the secondary transfer nip portion is the fixing nip portion (first nip portion) of the first fixing device 100. ) It is fixed by being heated and pressurized at N1.

  The paper P exiting the first fixing device 100 is introduced into the second fixing device 200 by the transport unit c. The toner image Tb fixed on the sheet (FIG. 6) is heated and pressed again at the fixing nip portion (second nip portion) N2 of the second fixing device 200, so that the surface shape becomes smooth. A uniform glossy image can be obtained.

  When the sheet P exits the second fixing device 200 is in the single-sided printing mode, it is guided by the flapper 15 to the conveyance unit d side, and is conveyed and discharged to the discharge tray 16 as a full-color image formed product of single-sided printing. The

  In the double-sided printing mode, the first-side printed paper P exiting the second fixing device 200 is guided to the reverse conveyance e side by the flapper 15. Then, the sheet is reversely fed by the switchback conveyance unit f, enters the conveyance unit a through the double-sided conveyance unit g, and is reintroduced into the secondary transfer nip unit in a state where the front and back sides are reversed. As a result, a toner image is formed on the second side of the paper P. Thereafter, the paper P is transported through the paths of the transport unit b, the first fixing device 100, the transport unit c, the second fixing device 200, and the transport unit d in the same manner as in the single-sided printing mode. A full color image formed product is conveyed and discharged to the tray 16.

  In the case of mono-color image formation, the image forming unit U necessary for forming the image performs an image forming operation, and the other image forming units do not perform the image forming operation only by the idling rotation of the photosensitive drum 3. .

  The transport units a to g are configured by transport members for transporting paper while guiding the paper. The conveyance member is a conveyance guide, a conveyance roller, a belt conveyance device, or the like.

(2) Control Unit FIG. 3 is a schematic block diagram of the control system. The control unit A comprehensively controls the image forming apparatus 1. 3 mainly shows a power source unit (device power source: main body power source) D, an operation unit B, a host device C, first and second fixing devices 100 and 200, an exhaust fan F1, a blower fan F2, and an air flow generation described later. Only the portion related to the transport unit fan F3 as means is shown.

  The power supply unit D is connected to the CPU 20 of the control unit A through the power supply control unit 22 and receives power supply via the plug 30 inserted into the outlet 29 of the commercial AC power supply AC to constitute the image forming apparatus 1. Power is supplied to various units (process equipment). The power supply unit D converts the voltage of AC power obtained from the commercial AC power source AC into a voltage suitable for each unit, and converts AC to DC as necessary depending on the unit to which power is supplied.

  MSW is a main power switch of the image forming apparatus 1 and is turned ON / OFF by an operator. The power source D is turned on / off by the ON / OFF operation of the switch MSW. That is, the apparatus is turned on and off.

  The operation unit B is connected to the CPU 20 via the I / F unit 24. The operation unit B is a user interface (UI: User Interface, manual operation unit) for setting an image forming mode and inputting various instructions from the operator, and notifying the state of the apparatus to the operator. The operation unit B includes an input unit Ba and a display unit Bb. Various operation keys and the like (not shown) are arranged in the input unit Ba. The display unit Bb is a touch panel type liquid crystal screen (not shown), which displays various types of information and various operation buttons. Various settings of operations performed by the image forming apparatus 1 are also input by the displayed operation buttons.

  The host device C is connected to the CPU 20 via the I / F unit 23, and image formation information (print job: print signal) is input to the CPU 20. This is processed between the image processing unit 27, the RAM 25, and the ROM 26 to form an image. Various settings of operations performed by the image forming apparatus 1 can also be input to the control unit A via a UI screen (not shown) of the host apparatus C. The first and second fixing devices 100 and 200 and the fans F1, F2, and F3 are controlled by the controller 21 of the CPU 20 in a predetermined manner.

(3) Operation Sequence of Image Forming Apparatus FIG. 4 is an operation sequence diagram of the image forming apparatus 1.

a. Initial rotation operation (front multiple rotation process)
This is a start-up operation period (start-up operation period, warm-up period) executed when the main power switch MSW of the image forming apparatus 1 is turned on (when the apparatus is turned on). When the main power switch MSW is turned on, the control unit A activates the main motor M to drive the photosensitive drum 3 and the intermediate transfer belt unit 9 of each image forming unit U in the image forming unit 2. In addition, a preparatory operation for a predetermined process device such as start-up of the first and second fixing devices 100 and 200 to a predetermined temperature is executed.

b. Print preparation rotation operation (pre-rotation process)
This is the preparatory rotation operation period before image formation from when the print signal (print job) is input until the actual image formation (printing) process operation is performed. When the print signal is input during the initial rotation operation, the initial rotation operation is performed. It is executed following to. When no print signal is input, the driving of the main motor M is temporarily stopped after the initial rotation operation is completed. As a result, the photosensitive drum 3 and the intermediate transfer belt unit 9 of each image forming unit U are stopped, and the image forming apparatus 1 is kept in a standby (standby) state until a print signal is input. When a print signal is input, a print preparation rotation operation is executed.

c. Printing process (image forming process, image forming process)
When the predetermined print preparation rotation operation is completed, the photosensitive drum 3 and the intermediate transfer belt unit 9 of each image forming unit U are subsequently driven to form toner images on the paper P, and the first and second fixing devices 100. A toner image fixing process 200 is performed. That is, the print job is executed and the image formed product is printed out. In the continuous printing (continuous printing) mode, the above printing process is repeated for a predetermined set number of prints n.

d. Inter-paper step This is a period from the end of the formation of the toner image corresponding to one paper P to the start of the formation of the toner image corresponding to the next paper P in the continuous printing mode.

e. Post-rotation operation After the printing process of the last sheet P is completed, the main motor M is continuously driven for a while to drive the photosensitive drum 3 and the intermediate transfer belt unit 9 of each image forming unit U, and a predetermined post-operation It is a period to execute.

f. Standby When the predetermined post-rotation operation is completed, the driving of the main motor M is stopped, and the driving of the photosensitive drum 3 and the intermediate transfer belt unit 9 of each image forming unit U is stopped. In this state, the image forming apparatus 1 is kept in a standby state as a standby mode that waits for the start of image formation until the next print signal is input.

  In the case of printing only one sheet, after the printing is completed, the image forming apparatus 1 enters a standby state through a post-rotation operation. When a print signal is input in the standby state, the printer proceeds to a pre-rotation process.

(4) First and Second Fixing Devices FIG. 5 is a schematic cross-sectional view showing the configuration of the first fixing device 100 of the tandem fixing unit in the image forming apparatus of this embodiment, and FIG. It is a cross-sectional schematic diagram which shows the structure of these. The first and second fixing devices 100 and 200 are positioned in a relationship between the upstream side and the downstream side with respect to the paper transport direction (recording material transport direction) X. In this embodiment, the first fixing device 100 is a so-called belt fixing device using a fixing roller and a pressure belt (fixing belt). The second fixing device 200 is a so-called roller pair fixing device using a fixing roller and a pressure roller.

  The first fixing device 100 includes a fixing roller (first roller) as a first pair of rotating bodies that form a first nip portion (fixing nip portion) N1 for heating the paper P conveyed from the image forming portion 2. 1 heating rotating body) 40 and a pressure belt (first pressing rotating body) 41. The pressure belt 41 is a flexible endless belt.

  The second fixing device 200 includes a fixing roller 52 as a second pair of rotating bodies that form a second nip portion (fixing nip portion) N2 for heating the paper P that has exited the first fixing device 100. And a pressure roller 531. The second fixing device 200 sandwiches and conveys the paper P carrying the fixed toner image Tb introduced from the first fixing device 100 in the fixing nip N2. As a result, the gloss is improved by reheating and pressurizing the fixed toner image Tb to smooth the surface.

  In the first fixing device 100 of FIG. 5, the fixing roller 40 includes a cored bar made of a cylindrical metal (made of aluminum in this embodiment) having an outer diameter of 77 mm, a thickness of 6 mm, and a length of 350 mm. On this mandrel, as a heat-resistant elastic layer, silicone rubber (JIS-A hardness 20 degrees in this embodiment) is coated with a thickness of 1.5 mm. Further, on the elastic layer, a fluororesin (in this embodiment, a PFA tube) is coated with a thickness of 50 μm as a heat-resistant release layer in order to improve releasability with the toner.

  The fixing roller 40 is rotatably supported with respect to the fixing device frame 100A, and the driving force of the main motor M is transmitted through a drive transmission mechanism (not shown), and a predetermined speed, for example, 500 mm / sec. Is rotated in the direction of arrow R40 at a peripheral speed of.

  In addition, a halogen heater 43a having a rated power of 1200 W, for example, is disposed as a heating element inside the cored bar of the fixing roller 40. The halogen heater 43 a generates heat upon receiving power supply from the power supply unit 31 controlled by the controller 21. The heat generation heats the fixing roller 40 from the inside, and the surface temperature of the fixing roller 40 is detected by a temperature sensor (thermistor) 44a. The detected temperature information is input to the controller 21.

  The controller 21 controls the power supplied from the power supply unit 31 to the halogen heater 43a so as to maintain the surface temperature of the fixing roller 40 at a predetermined temperature so that the input detected temperature information is maintained at the temperature information corresponding to the predetermined set temperature. Adjust.

  A pressure belt unit 45 is disposed below the fixing roller 40. The pressure belt unit 45 includes an entrance roller 46, a separation roller 47, a steering roller 48, and a pressure pad 49, and the pressure belt 41, which is an endless belt, is stretched between these members.

  The pressure belt 41 is formed by coating a polyimide base layer having a thickness of 100 μm with a 200 μm-thick silicone rubber layer and having an outer diameter of φ70. The separation roller 47 and the pressure pad 49 are pressurized toward the fixing roller 40 via the pressure belt 41 by a pressure mechanism (spring: not shown). As a result, the pressure belt 41 is in wide contact with the fixing roller 40 in the sheet conveyance direction X to form the fixing nip portion N1. In this embodiment, 490 N (50 kgf) is applied to the pressure pad 49 and 490 N (50 kgf) is applied to the separation roller 47.

  The driving force of the main motor M is transmitted to the separation roller 47 via a drive transmission mechanism (not shown), and the pressure belt 41 is in a direction indicated by an arrow R41 at a predetermined peripheral speed corresponding to the rotational peripheral speed of the fixing roller 40. It is configured to rotate in the direction.

  Inside the entrance roller 46, a halogen heater 43b having a predetermined rated power is disposed as a heating element. The halogen heater 43 b generates heat upon receiving power supply from the power supply unit 31 controlled by the controller 21. The entrance roller 46 is heated from the inside by the heat generation, and the pressure belt 41 is heated by the heat of the entrance roller 46. The surface temperature of the pressure belt 41 is detected by the temperature sensor 44b.

  The detected temperature information is input to the controller 21. The controller 21 controls the power supplied from the power supply unit 31 to the halogen heater 43b so that the input detected temperature information is maintained at the temperature information corresponding to the predetermined set temperature, thereby setting the surface temperature of the pressure belt 41 to a predetermined value. Adjust the temperature. The predetermined set temperature is set in such a range that the gloss difference between the first side and the second side during the fixing operation on both sides is not widened, and the temperature is not greatly lowered by pressing the fixing roller 40.

  The sheet P introduced into the fixing nip portion N1 and being nipped and conveyed exits the fixing nip portion N1 and is discharged and conveyed from the first fixing device 100 by the paper discharge unit 50. The paper discharge unit 50 includes an air nozzle 50 a as a paper separation auxiliary device from the surface of the fixing roller 40, and a separation claw 50 b as a paper separation auxiliary device from the surface of the pressure belt 41. In addition, a conveyance guide (guide member) 50c for receiving and guiding the paper P discharged from the fixing nip portion N1 and a discharge roller pair 50d are provided. The sheet P guided by the conveyance guide 50c is conveyed by the conveyance unit c to the fixing nip portion N2 of the second fixing device.

  In the second fixing device 200 of FIG. 6, the fixing roller 52 is a hollow roller having the same configuration as the fixing roller 40 in the first fixing device 100. The fixing roller 52 is rotatably supported with respect to the fixing device frame 200A, and the driving force of the main motor M is transmitted through a drive transmission mechanism (not shown), and a predetermined speed, for example, 500 mm / sec. It is rotationally driven in the direction of arrow R52 at the peripheral speed.

  In addition, a halogen heater 54 a with a rated power of 1200 W, for example, is disposed as a heating element inside the cored bar of the fixing roller 52. The halogen heater 54 a generates heat upon receiving power supply from the power supply unit 31 controlled by the controller 21. The heat generation heats the fixing roller 52 from the inside, and the surface temperature of the fixing roller 52 is detected by the temperature sensor 55a. The detected temperature information is input to the controller 21. The controller 21 controls the power supplied from the power supply unit 31 to the halogen heater 54a so as to maintain the surface temperature of the fixing roller 52 at a predetermined temperature so that the input detected temperature information is maintained at the temperature information corresponding to the predetermined set temperature. Adjust.

  Under the fixing roller 52, an elastic pressure roller 53 is parallel to the fixing roller 52 and is elastically applied to both rollers with a predetermined pressing force toward the fixing roller 52 by a pressure mechanism (spring: not shown). Pressurized against the elasticity of As a result, the pressure roller 53 is pressed against the fixing roller 52 in the sheet conveyance direction X to form a fixing nip portion N2 having a predetermined width. In this embodiment, the pressure roller 53 is rotated in the direction of the arrow R53 following the rotational driving of the fixing roller 52. An apparatus configuration that also drives the pressure roller 53 may be employed.

  The image-fixed paper P exiting the first fixing device 100 is transported by the transport unit c and introduced into the second fixing device 200, and is subjected to reheating and pressing of the fixed toner image Tb.

(5) Fan and its Control In the first fixing device 100, the atmosphere around the fixing roller 40 and the pressure belt 41 is set in the vicinity of the fixing roller 40 and the pressure belt 41 which are the first pair of rotating bodies. An exhaust fan F1 that discharges outside the apparatus is provided. In the present embodiment, an exhaust fan F1 for discharging hot air generated in the first fixing device 100 to the outside of the first fixing device 100 is provided above the first fixing device 100 and in the vicinity of the first fixing device 100. It has been.

  In this embodiment, the exhaust fan F1 is an axial fan having a maximum air volume of about 4 cubic meters / minute. The exhaust fan F1 is connected to an exhaust duct (not shown) that communicates with the outside of the image forming apparatus 1, and the exhaust duct guides the heated exhaust to the outside of the apparatus.

  Further, a blower fan F <b> 2 is provided on the downstream side of the first fixing device 100 in the sheet conveyance direction X. The blower fan F2 blows outside air toward a predetermined component of the first fixing device 100, in this embodiment, the pressure belt unit 45, and blows air toward the conveyance guide 50c of the paper discharge unit 50.

  In this embodiment, the blower fan F2 is a sirocco fan having a maximum air volume of about 1.4 cubic meters / minute. The blower fan F2 is connected to a fan duct (not shown) that communicates with the outside of the image forming apparatus 1, and the fan duct guides room temperature air (outside air) outside the apparatus to the blower fan F2. The blower fan F2 blows air toward the pressure belt unit 45 and the paper discharge unit 50 using the outside air as cold air.

  The conveyance unit c that conveys the paper P from the first fixing device 100 to the second fixing device 200 serves as a conveyance member made of stainless steel and a conveyance roller that nips and conveys the paper P as a conveyance member. (Not shown). In addition, a conveyance path fan F3 as an air flow generating means for generating an air flow toward the fixing nip portion N2 of the second fixing device 200 is disposed along the conveyance unit c. The conveyance path fan F3 blows air toward the conveyance guide 51 of the conveyance unit c. The conveyance guide 51 includes a passage portion 51a that allows the air from the conveyance path fan F3 to pass toward the fixing nip portion N2.

  In the present embodiment, the transport unit fan F3 is an axial fan with a maximum air volume of about 0.6 cubic meters / minute, and blows in-machine air (air in the machine) to the transport unit c.

  The operations of the exhaust fan F1, the blower fan F2, and the conveyance path fan F3 are controlled by the controller 21 of the control unit A. FIG. 1 is a control flowchart of the three fans F1E, F2, and F3 in the present embodiment.

  When the power of the image forming apparatus 1 is turned on (main power switch MSW-ON: when the apparatus is turned on), the controller A turns off all the fans F1E, F2, and F3 (step S1). Then, when the power of the image forming apparatus 1 is turned on, the control unit A is located downstream of the fixing nip portion N1 of the first fixing device 100 in the paper conveyance direction, and conveyance guides 50c and 51 that are to take measures against condensation. The information about the temperature of the is acquired by the acquisition unit.

  If the inside of the apparatus is cold, it can be said that the conveyance guides 50c and 51 are also cold. In this embodiment, the control unit A refers to the value of the surface temperature of the fixing roller 40 of the first fixing device 100 in order to determine whether or not the inside of the apparatus is cold. That is, the surface temperature value of the fixing roller 40 is detected from the temperature detection information input to the controller 21 from the temperature sensor 44a (S2).

  In this embodiment, whether or not to perform dew condensation countermeasure control for the conveyance guides 50c and 51 is determined depending on whether or not the surface temperature of the fixing roller 40 is 50 ° C. or higher (the output temperature of the temperature sensor 44a) (S2). (S4 or S8).

  In step S3, when the output temperature of the temperature sensor 44a at the time of power ON is 50 ° C. or higher, the controller A has a sufficiently high temperature in the machine and does not need to perform dew condensation countermeasure control of the transport guides 50c and 51. to decide. Then, during the warming up of the image forming apparatus, control is performed to turn on the exhaust fan F1, the blower fan F2, and the transport unit fan F3 (S8).

  As shown in FIG. 7, the in-machine air flow during the fan control (S8) is dominated by the flow toward the pressure belt unit 45 by the blower fan F2 and the upward flow by the exhaust fan F1. Therefore, the hot air generated in the first fixing device 100 is discharged upward in the vertical direction.

  Here, the temperature threshold value for determining whether or not the inside of the apparatus is cold is preferably lower than the target value of the surface temperature of the fixing roller 40 at the time of printing and higher than the normal temperature. In this embodiment, the temperature sensor 44a refers to the surface temperature at the center in the longitudinal direction of the fixing roller 40, but the temperature at the end in the longitudinal direction may be referred to. Further, the surface temperature of the pressure belt 41 may be referred to by the temperature sensor 44b. That is, the information on the temperature of the conveyance guides (guide members) 50c and 51 can be output information from the temperature sensors 44a and 44b that detect the temperature of either the fixing roller 40 or the pressure belt 41.

  On the other hand, if the output temperature of the temperature sensor 44a when the power is turned on is lower than 50 ° C. in step S3, the control unit A determines that the inside of the apparatus is cold. That is, it is determined that the conveyance guides 50c and 51 are also cold and it is necessary to perform dew condensation countermeasure control. Then, during the warm-up and standby state of the image forming apparatus, control is performed to turn off the exhaust fan F1 and the blower fan F2 and turn on the transport unit fan F3 (S4).

  If the device is warming up in step S4 or is in a standby state, the air in the machine is directed toward the transport section c by the fan control until a certain time has passed since the power was turned on. Let spray. Therefore, the hot air generated in the first fixing device 100 moves in the direction of α shown in FIG.

  By the movement of the hot air, the conveyance guide 50c in the paper discharge unit 50 of the first fixing device 100 can be efficiently warmed. In addition, the conveyance guide 51 of the conveyance unit c can be efficiently warmed. Thereby, the temperature of the conveyance guides 50c and 51 can be efficiently raised using the heat generated in the first fixing device 100 without providing a dedicated heating member. Therefore, it is possible to suppress dew condensation on the conveyance guides 50c and 51 without complicating the apparatus.

  When the warm-up is completed and the printer shifts to a standby state and a print job is executed (YES in S5), the process shifts to step S8 to control to turn on the exhaust fan F1 and the blower fan F2 that are turned off. Made. If the print job is not executed in step S5, the standby state is continued (S6).

  Then, when a predetermined time, 30 minutes in this embodiment, has elapsed since the power ON step (YES in S7), the process proceeds to step S8, where control is performed to turn on the exhaust fan F1 and the blower fan F2 that are turned off. Made. If it has not elapsed, the process proceeds to step S5.

  That is, when it is in an environment where condensation easily occurs in the morning, the operation of the exhaust fan F1 and the blower fan F2 is stopped (S4). Accordingly, the hot air movement of the first fixing device 100 due to the air flow of the transport fan F3 quickly warms the guide member 50c and the guide member 51, which are likely to cause dew condensation, and prevents an abnormal image from appearing during the morning print job.

  In this embodiment, the operation of the exhaust fan F1 and the blower fan F2 is turned off for 30 minutes after the image forming apparatus 1 is turned on. Further, it is preferable to turn on the exhaust fan exhaust heat fan F1 and the cooling fan F2 so that the water vapor generated from the paper does not fill the vicinity of the paper discharge unit 50 of the first fixing device 100 during printing.

  The above fan control is summarized as follows. It has the acquisition part 44a which acquires the information regarding the temperature of the conveyance guides 50c and 51. FIG. When the above information indicates that the conveyance guides 50c and 51 are at a predetermined temperature or higher when the apparatus is turned on, the control unit A turns on the conveyance path fan F3 during the warm-up of the fixing apparatus 100. In addition, control is performed to turn on the exhaust fan F1. Further, when the above information indicates that the conveyance guides 50c and 51 are below a predetermined temperature, during the warming up of the fixing device 100, the conveyance path fan F3 is turned on and the exhaust fan F1 is turned off.

  When the above information indicates that the conveyance guides 50c and 51 are at a predetermined temperature or higher when the apparatus is turned on, the control unit A controls to turn on the blower fan F2 during warming up of the fixing apparatus 100. I do. When the above information indicates that the conveyance guides 50c and 51 are below a predetermined temperature, the blower fan F2 is controlled to be turned off during the warming up of the fixing device 100.

The control unit A performs control to turn on the exhaust fan F1 when executing a print job. The control unit A performs control to turn on the blower fan F2 when executing a print job. The control unit A performs control to turn on the exhaust fan F1 after a predetermined time has elapsed in the standby state of the image forming apparatus. The control unit A performs control to turn on the blower fan F2 after a predetermined time has elapsed in the standby state of the image forming apparatus.
The controller A turns off the exhaust fan F1 and the blower fan F2 until a predetermined time elapses or until a print job is started. The predetermined time is a time during which the conveyance guides 50c and 51 are not cooled to the temperature at which condensation occurs even if the heat exhaust fan F1 and the blower fan F2 are turned on in the non-sheet passing state. In this embodiment, the predetermined time is set to 30 minutes. In the image forming apparatus of this embodiment, since warm-up is 10 minutes, standby is continued for 20 minutes.

  When the warm-up for 10 minutes is completed, the print job can be executed, and the exhaust fan F1 and the blower fan F2 are turned on during the print job. Further, if the warm-up is continued for 10 minutes and the apparatus is on standby, the exhaust fan F1 and the blower fan F2 are kept OFF for +20 minutes.

  The reason is as follows. It is assumed that the temperature of the conveyance guides 50c and 51 where condensation occurs is less than 50 ° C., and the temperature of the conveyance guides 50c and 51 immediately after the completion of warming is 60 ° C. When a print job is executed immediately after the warm-up is completed, the conveyance guides 50c and 51 are cooled by the blower fan F2, but are warmed in contact with the warm paper immediately after fixing. That is, the increase and decrease in temperature are offset and 60 ° C. can be maintained. Even if printing is started in this state, condensation does not occur. Since water vapor is emitted from the paper during printing, the blower fan F2 is turned on to disperse the water vapor.

  On the other hand, if the blower fan F2 is turned on immediately after the warm-up is completed, the transport guides 50c and 51 are cooled by the blower fan F2, so that the temperature decreases from 60 ° C. to around 40 ° C. When printing is started in this state, condensation occurs.

  On the other hand, the conveyance guides 50c and 51 are 80 ° C. 20 minutes after the warm-up is completed (a predetermined time after the power is turned on). In this state, even if the blower fan F2 is turned on, the conveyance guides 50c and 51 can be lowered only to about 60 ° C. Even when printing is started in this state, no condensation occurs.

  FIG. 9 shows the time transition of the surface temperature of the conveyance guides 50c and 51 when the image forming apparatus 1 is turned on and the sheet is passed immediately after completion of standby.

  When both the exhaust fan F1 and the blower fan F2 in (A) are turned off, the surface temperature of the transport guides 50c and 51 is higher than when both the exhaust fan F1 and the blower fan F2 are turned on in (B). Can be seen to rise quickly.

  While the sheet is passing, the temperature decreases because the sheet P passes along the surfaces of the conveyance guides 50c and 51. The lowest point of the surface temperature of the conveyance guides 50c and 51 in this case (A) is , (B), it is about 10 ° C. higher than the lowest point of the surface temperature of the conveyance guides 50c, 51. That is, in the case of (A), the temperature of the surfaces of the conveyance guides 50c and 51 is sufficiently increased, so that the phenomenon that water vapor is condensed on the surfaces of the conveyance guides 50c and 51 can be suppressed as compared with the case of (B). .

  Therefore, immediately after the power of the image forming apparatus is turned on, even if the sheet P is passed while the temperature in the apparatus is still low, the toner image is disturbed by the condensation of the conveyance guides 50c and 51, and an abnormal image is generated. The phenomenon can be suppressed.

《Other matters》
(1) An apparatus configuration in which the blower fan F2 is omitted may be employed. In this case, the control unit A operates the exhaust fan F1 until a predetermined time elapses when the temperature inside the apparatus is equal to or lower than a predetermined temperature prior to the start of paper introduction when the apparatus is turned on. Stop.

  (2) In the above-described embodiment, the determination of the temperature state in the apparatus when the apparatus power is turned on (acquisition of information on the temperature of the guide members 50c and 51) is performed using the surface temperature of the fixing roller 40 of the first fixing apparatus 100. Although it is based on the detected temperature, it is not limited to this. The detection may be performed based on the detected temperature of the surface temperature of either the pressure belt 41 of the first fixing device 100 or the fixing roller 52 or the pressure roller 53 of the second fixing device 200. Moreover, you may perform based on the detection temperature of the temperature sensor which detects the detection temperature of another apparatus member, and the atmospheric temperature in a machine.

  (3) The first fixing device 100 may be a roller pair fixing device, and the second fixing device 100 may be a belt fixing device. Both of them may be a roller pair fixing device or a belt fixing device. The first fixing device 100 and the second fixing device 100 may be configured such that both the heating rotator and the pressure rotator are endless belts. The heating configuration of the heating rotator and the pressure rotator is not limited to a configuration using a halogen heater. An electromagnetic oscillation heating configuration or the like may be used.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 1A ... Apparatus main body, 2 ... Image forming part, 100 ... First fixing device, N1, ... First nip part (fixing nip part), 200 ... Second fixing Device, N2... Second nip (fixing nip), c.. Conveying section, P .. Recording material, Ta .. Unfixed toner image, Tb .. Fixed toner image, F1. , F2 ・ ・ Blower fan, F3 ・ ・ Conveyor fan, A ・ ・ Control unit

Claims (8)

An image forming unit for forming a toner image on a recording material;
A first pair of rotators that form a first nip for heating the recording material conveyed from the image forming unit;
A second pair of rotating bodies forming a second nip portion for heating the recording material conveyed from the first nip portion ;
A guide member for receiving and guiding the recording material discharged from the first nip portion ;
A transport unit that transports the recording material guided by the guide member to the second nip portion;
An air flow generating means for generating an air flow toward the second nip portion along the transport section ;
An exhaust fan that is provided in the vicinity of the first pair of rotating bodies and exhausts the atmosphere around the first pair of rotating bodies to the outside of the apparatus;
An acquisition unit for acquiring information on the temperature of the guide member;
When the information indicates that the guide member is at a predetermined temperature or higher when the apparatus is turned on, the air flow generating means is turned on and the exhaust gas is exhausted during warming up of the first pair of rotating bodies. When the information indicates that the guide member is below a predetermined temperature, the air flow generating means is turned on and the exhaust is turned on during warming up of the first pair of rotating bodies. An image forming apparatus comprising: a control unit that performs control to turn off the fan.   A blower fan that blows air toward the guide member; and when the information indicates that the guide member is at a predetermined temperature or higher when the power of the apparatus is turned on, the first pair If the information indicates that the guide member is lower than a predetermined temperature, the air blower is turned on during the warming up of the first pair of rotating bodies. The image forming apparatus according to claim 1, wherein the fan is turned off. The image forming apparatus according to claim 2 , wherein the control unit performs control to turn on the blower fan when executing a print job . The image forming apparatus according to claim 2 , wherein the control unit performs control to turn on the blower fan after a predetermined time has elapsed in a standby state of the image forming apparatus. 5. The information on the temperature of the guide member is output information from a temperature sensor that detects the temperature of any one of the first pair of rotating bodies. 6. The image forming apparatus described in 1. The conveyance unit includes a conveyance member, and the airflow generation unit is a fan that blows air toward the conveyance member, and passes through the conveyance member so that air from the fan passes toward the second nip portion. the image forming apparatus according to any one of claims 1 to 5, characterized in that it has a part. The image forming apparatus according to claim 1, wherein the control unit performs control to turn on the exhaust fan when executing a print job . Wherein the control unit, the image forming apparatus according to any one of claims 1 to 7, characterized in that the control of the ON said exhaust fan at a predetermined time elapses in the standby state of the image forming apparatus.