JP2007171476A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of securely preventing a decrease in image quality due to a rise in temperature in the apparatus with simple configuration. <P>SOLUTION: When continuous printing of recording paper A is performed in one-surface printing mode or both-surface printing mode, if a count value of a counter counting successively printed sheets of recording paper A reaches a predetermined value, the printing operation is temporarily stopped, the one-surface printing mode or both-surface side printing mode is changed to a cooling mode, and a second changeover guide 82 and a third changeover guide 84 are switched as shown by solid lines. In the cooling mode, cooling paper B fed from a paper feed tray 80 and carried to a nip part between a driving roller 56 and a secondary transfer roller 57 absorbs heat from an intermediate transfer belt 55 contacting the cooling paper B when passing through the nip part, and consequently while the intermediate transfer belt 55 is cooled, a photosensitive drum 50 pressed against the intermediate transfer belt 55 and a developing unit 53 installed nearby the photosensitive drum 50 are cooled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer.

  Conventionally, image forming apparatuses such as copying machines and printers are known. In this image forming apparatus, a charging process for charging the surface of the photosensitive drum, an exposure process for irradiating the charged photosensitive drum with laser light to form an electrostatic latent image on the surface of the photosensitive drum, and a surface formed on the surface of the photosensitive drum. Development process for developing toner by attaching toner to the electrostatic latent image, transfer process for transferring the toner attached to the surface of the photosensitive drum to the recording paper, and fixing process for fixing the transferred toner to the recording paper Are sequentially performed, so that an image is printed on the recording paper.

  In the image forming apparatus having such a configuration, when continuous printing of recording paper is performed, the temperature in the machine increases as the number of continuous printing increases due to heat radiation from the heated recording paper to fix the toner in the fixing step. As the temperature rises, the developing unit or the like in which the toner is accommodated is heated. In addition, in an image forming apparatus having both a single-sided printing mode and a double-sided printing mode, when the recording paper is continuously printed in the double-sided printing mode, the other side of the heated recording paper after the single-sided printing is printed. Therefore, when the recording paper transported passes through the installation position of the photosensitive drum, the toner is transferred to the high-temperature recording paper and the photosensitive drum absorbs the heat of the recording paper and is heated.

  When the photosensitive drum or the developing unit is heated in this way, the quality of the toner stored in the developing unit is changed, so that the quality of the image printed on the recording paper is deteriorated and the toner adheres to the surface of the photosensitive drum. The properties of the toner to be changed may change, which may reduce the quality of the image transferred to the recording paper. Also, if the temperature of the transfer surface when the image is transferred to one side of the recording paper and the temperature of the transfer surface when the image is transferred to the other side of the recording paper on which one side is printed differ greatly, There is a clear difference in the quality of the images printed on each side of the paper.

  On the other hand, after measuring the temperature inside the machine using the temperature sensor inside the machine and temporarily stopping the printing operation when the temperature inside the machine exceeds a predetermined value, cooling the inside of the machine using a cooling fan etc. An image forming apparatus has been developed that performs control to resume the printing operation after confirming that the temperature inside the apparatus has sufficiently decreased.

  In addition, a sheet having a plurality of cooling fans and a guide plate in a sheet conveyance path for conveying the recording sheet to the registration roller in order to print the second surface of the recording sheet on which the first surface is printed in the duplex copying mode. A conveyance cooling unit is installed, and the recording paper on which the first surface is printed is cooled by air outside the apparatus by controlling the number of rotations and on / off of the plurality of cooling fans based on the temperature information of the temperature sensor. There has been proposed an image forming apparatus configured such that a temperature before transfer of a recording sheet onto which an image is transferred falls within a predetermined range (see Patent Document 1).

Furthermore, the FD motor drive system that drives the conveyance roller that discharges the recording paper on which the image is printed to the outside of the apparatus is used to cool the unit that wants to reduce the influence of the temperature rise caused by the heat generated in the power supply unit or the image fixing device. By connecting power using a fan windmill drive mechanism and a one-way clutch and gear, the number of parts can be reduced and the structure can be simplified without providing a drive mechanism dedicated to the cooling fan windmill. An image forming apparatus capable of performing the above has been proposed (see Patent Document 2).
JP 2004-157369 A JP 2000-162932 A

  However, in the above-described image forming apparatus that controls the printing operation according to the temperature inside the machine, the temperature inside the machine is sufficiently lowered and the printing operation is restarted after the temperature inside the machine exceeds a predetermined value and the printing operation is stopped. Since it takes a long time to be performed, there is a problem that the usability of the apparatus is deteriorated.

  Further, in the image forming apparatus disclosed in Patent Document 1, since a sheet conveyance cooling unit including a plurality of cooling fans and guide plates is installed in the sheet conveyance path, components inside the apparatus are set when setting the sheet conveyance path. There is a problem that the layout of the apparatus is restricted and the configuration of the apparatus is complicated.

  Furthermore, in the image forming apparatus disclosed in Patent Document 2, the FD motor drive system that drives the transport roller and the drive mechanism of the cooling fan wind turbine are connected to each other, so that the transport roller that rotates at a predetermined speed is connected. The rotational speed of the cooling fan wind turbine is also constant. Here, during double-sided printing, the distance that the recording paper after single-sided printing heated by the image fixing device is conveyed through the apparatus is longer than during single-sided printing. Then, heat is dissipated while the recording paper is transported in the apparatus, so that the temperature in the apparatus becomes higher during double-sided printing than during single-sided printing. However, in this image forming apparatus, since the rotation speed of the cooling fan wind turbine is constant, there is a possibility that the unit inside the apparatus cannot be sufficiently cooled during duplex printing.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can reliably prevent a reduction in image quality due to a temperature rise inside the apparatus with a simple configuration. There is.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a sheet storage unit that can store a large number of sheets, and prints an image on a sheet fed from the sheet storage unit. A printing mode for printing an image on a sheet fed from the sheet storage unit, and a cooling mode for cooling the member by absorbing heat of the member that transfers the image to the sheet fed from the sheet storage unit. And when the images are continuously printed on the paper, the printing operation is temporarily stopped when the predetermined timing is reached after the printing operation in the printing mode is started, and the cooling mode is changed from the printing mode to the cooling mode. , And after the paper fed from the paper container passes through the installation position of the member, the cooling mode is returned to the printing mode.

  In addition, as a member for transferring an image, in a system in which the toner attached to the surface of the photosensitive drum is directly transferred to the paper, the toner attached to the surface of the photosensitive drum is transferred to the paper via the intermediate transfer belt. An intermediate transfer belt is an example of the transfer type.

  The image forming apparatus configured as described above includes a counter that counts the number of continuously printed sheets, and the predetermined timing is determined based on the number of continuously printed sheets counted by the counter.

  Here, as the number of continuously printed sheets increases, the temperature of the member that transfers the image to the sheet fed from the sheet storage unit and the temperature inside the apparatus increase. Therefore, every time the count value by the counter reaches a predetermined value, the paper printing operation is temporarily stopped, and the printing mode is changed to the cooling mode. For example, when printing images continuously on 100 sheets of paper, the print mode is switched to the cooling mode every time 10 sheets are printed, that is, every time the counter value reaches a multiple of 10. Then, one or a plurality of predetermined sheets are fed from the sheet storage unit and conveyed toward the installation position of the member for transferring the image. When the cooling operation in the cooling mode is completed, the paper printing operation in the interrupted print mode is resumed.

  The image forming apparatus configured as described above may include a timer for measuring the continuous printing time of the paper, and the predetermined timing may be determined based on the continuous printing time of the paper measured by the timer. I do not care.

  In each of the image forming apparatuses described above, a fixing unit that fixes an image on a sheet onto which an image that has passed through the installation position of the member is transferred in the printing mode, and a conveyance direction of the paper that has passed through the installation position of the member A switching member for switching between the print mode and the cooling mode, and the direction of conveyance of the sheet that has passed through the installation position of the member is switched by the switching member in the cooling mode. The sheet that has passed the installation position is prevented from being conveyed to the fixing unit.

  In this way, the fixing member necessary for fixing the image on the sheet is operated by operating the switching member and preventing the sheet passing through the installation position of the member for transferring the image in the cooling mode to the fixing unit. It is possible to prevent the heat from being taken away by the paper, and it is possible to shorten the time required to return from the cooling mode to the printing mode.

  In the image forming apparatus configured as described above, the paper storage unit includes a first paper storage unit and a second paper storage unit, and in the print mode, paper is fed from the first paper storage unit. At the same time, in the cooling mode, paper is fed from the second paper storage unit.

  Thereby, different types (size, material, etc.) of sheets can be stored in the first sheet storage section and the second sheet storage section, and the usability of the image forming apparatus can be improved. In addition, by storing a sheet having a high cooling effect in the second sheet storage unit, it is possible to reliably cool the member to which the image is transferred, and to reliably prevent deterioration in image quality due to the heat of the member. In addition, it is possible to reliably prevent a decrease in image quality due to a temperature rise inside the apparatus.

  At this time, in the cooling mode, the sheet that has passed the installation position of the member is conveyed to the second sheet storage unit, is stored in the second sheet storage unit, and is fed again.

  Accordingly, the paper stored in the second paper storage unit can be repeatedly used to cool the member that transfers the image, and the amount of paper that is used to cool the member that transfers the image is reduced. can do.

  In any one of the above-described image forming apparatuses, the printing mode includes a single-sided printing mode for printing only one side of the paper and a double-sided printing mode for printing on both sides of the paper, and the single-sided printing mode and the double-sided printing The predetermined timing may be different from the mode.

  Here, in the double-sided printing mode, the paper after single-sided printing heated to fix the image on the paper passes through the installation position of the member to which the image is transferred again, so that the other side of the paper on which the single-sided printing is performed. The image is transferred to the surface. And when the member which transfers an image and the paper after single-sided printing contact, the member which transfers an image with the paper after single-sided printing is heated. In the double-sided printing mode, the distance that the paper after single-sided printing heated to fix the image on the paper is transported in the apparatus is longer than in the single-sided printing mode. Then, heat is dissipated while the sheet is transported in the apparatus, so that the temperature in the apparatus becomes higher in the double-sided printing mode than in the single-sided printing mode.

  In contrast, in the double-sided printing mode, it is possible to shift from the printing mode to the cooling mode at an earlier stage by advancing the predetermined timing than in the single-sided printing mode. It is possible to reliably prevent the image quality from being deteriorated due to the influence of the heat of the member to which the image is transferred, and to reliably prevent the image quality from being deteriorated due to the temperature rise inside the apparatus.

  According to the present invention, when images are continuously printed on paper, the printing operation is temporarily stopped when the predetermined timing is reached after the printing operation in the printing mode is started, and the printing mode is changed to the cooling mode. Then, the heat of the member that transfers the image is absorbed by the paper fed from the paper storage unit and the member is cooled, so that the influence of the heat of the member that transfers the image is made without complicating the configuration of the apparatus. It is possible to reliably prevent image quality degradation. Further, by cooling the image transfer member, the member in contact with the member is cooled, and the unit installed in the vicinity of the member and the member in contact with the member is also cooled. A reduction in image quality can be reliably prevented.

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

<< Embodiment of the Invention >>
The image forming apparatus of the present embodiment is configured to be able to output a color image or monochrome image composed of four colors of cyan, magenta, yellow, and black, and prints an image on one side of the recording paper A shown in FIG. A single-sided printing mode and a double-sided printing mode for printing images on both sides of the recording paper A shown in FIG.

  The image forming apparatus includes a cyan image forming unit 10 and a magenta image forming unit 20 as four image forming units for forming an image to be printed on the recording paper A, as indicated by a dashed frame in FIG. The yellow image forming unit 30 and the black image forming unit 40 are installed in order from the right side.

  As shown in FIG. 1, each of the cyan image forming unit 10, the magenta image forming unit 20, the yellow image forming unit 30, and the black image forming unit 40 has a uniform surface on the photosensitive drum 50 and the photosensitive drum 50. A charging unit 51 for charging the photosensitive drum 50, an exposure unit 52 for irradiating the surface of the photosensitive drum 50 with a laser beam emitted from a semiconductor laser (not shown), and a toner 53a on the electrostatic latent image formed on the surface of the photosensitive drum 50. In order to transfer the image formed on the surface of the photosensitive drum 50 onto the surface of the intermediate transfer belt 55 and press-contact with the photosensitive drum 50 via an intermediate transfer belt 55 described later. Primary transfer roller 54.

  As the exposure unit 52, a large number of LEDs arranged in a line on an LED head (not shown) can be used instead of the laser beam emitted from the semiconductor laser as described above. The surface of the photosensitive drum 50 may be irradiated with light emitted from an LED (not shown).

  As shown in FIG. 1, the image forming apparatus includes an intermediate transfer belt 55 on which images formed on the surface of the photosensitive drum 50 of each of the image forming units 10, 20, 30, and 40 are transferred. A plurality (two in FIG. 1) of driving rollers 56 that are in sliding contact with the back surface of the transfer belt 55 (that is, the surface opposite to the image transfer surface) and move the intermediate transfer belt 55 in the direction indicated by the arrow; A secondary transfer roller 57 for transferring an image formed on the surface of the intermediate transfer belt 55 to the recording paper A while being pressed against the driving roller 56 via the intermediate transfer belt 55 and an image transferred to the recording paper A And a fixing unit 60 as a fixing unit for fixing.

  Further, as shown in FIG. 1, the image forming apparatus accommodates a large number of recording papers A and is supplied as a first paper accommodating section configured to be detachable from the main body of the image forming apparatus. A paper cassette 70, a cassette-side paper feed roller 71 that feeds the recording paper A stored in the paper feed cassette 70 in order from the one placed on the upper side, and a recording paper fed from the cassette-side paper feed roller 71 A first conveyance roller 72 that conveys A toward a pair of registration rollers 73 described later, and a pair that corrects the orientation of the recording paper A that has passed through the first conveyance roller 72 and adjusts the timing at which the recording paper A is conveyed. The registration roller 73 and the pair of registration rollers 73 are conveyed toward a nip portion formed between the driving roller 56 and the secondary transfer roller 57 and the nip portion and the fixing unit 60. A paper discharge roller 74 that discharges the recording paper A that has passed through into the cylinder of the image forming apparatus, and a cylinder discharge that stacks the recording paper A that has passed through the paper discharge roller 74 and discharged into the cylinder of the image forming apparatus. For printing the paper tray 75, the first switching guide 76 for switching the transport direction of the recording paper A that has passed through the fixing unit 60, and the other side of the recording paper A on which one side is printed in the duplex printing mode. A plurality of (three in FIG. 1) second transport rollers 77 that transport the recording paper A toward the first transport roller 72 are installed.

  Then, the first switching guide 76 has a first surface of the recording paper A in the double-sided printing mode (hereinafter, the surface on which printing is performed first is referred to as “first surface”, and the surface on which printing is performed next to the first surface is described as “ 1 is switched to the direction indicated by the solid line in FIG. 1 when printing on the second side), and is switched to the direction indicated by the broken line in FIG. 1 when printing the second side of the recording paper A in the single-sided printing mode and the double-sided printing mode. .

  In the image forming apparatus having such a configuration, the charging unit 51 of each of the image forming units 10, 20, 30, and 40 includes the charging wire 51 a shown in FIG. 1, and the charging wire 51 a is close to the photosensitive drum 50. Installed in position. When a voltage having a predetermined magnitude is applied to the charging wire 51a, the surface of the photosensitive drum 50 is negatively charged by the discharge of the charging wire 51a. As shown in FIG. 1, the exposure unit 52 of each of the image forming units 10, 20, 30, 40 irradiates a laser beam from a semiconductor laser (not shown) toward the photosensitive drum 50. An electrostatic latent image is formed in this portion by positively charging the portion scanned with the laser beam 50.

  As shown in FIG. 1, the developing unit 53 of each of the image forming units 10, 20, 30, and 40 is installed in the vicinity of the photosensitive drum 50, and the toner 53a is accommodated therein and the toner 53a. Is provided with a developing roller 53 b for supplying the toner to the photosensitive drum 50. The developing unit 53 of the cyan image forming unit 10 has cyan (C) toner 53a, the developing unit 53 of the magenta image forming unit 20 has magenta (M) toner 53a, and the developing unit of the yellow image forming unit 30. 53, yellow (Y) toner 53a is accommodated in the developing unit 53 of the black image forming unit 40, and black (K) toner 53a is accommodated therein. The developing units 53 of the image forming units 10, 20, 30, and 40 perform development by attaching the toner 53 a to the electrostatic latent image formed on the surface of the photosensitive drum 50.

  Further, as shown in FIG. 1, the fixing unit 60 includes a fixing roller 61, a fixing heater 62 that is installed inside the fixing roller 61 and that heats the fixing roller 61, and a pressure roller 63. A nip portion that sandwiches the recording paper A is formed between the fixing roller 61 and the pressure roller 63. When the recording paper A passes through the nip portion, the fixing unit 60 dissolves the toner 53a attached to the recording paper A by the heat of the fixing roller 61 and applies pressure to the recording paper A by the pressure roller 63. As a result, the toner 53a is fixed to the recording paper A.

  Further, in the image forming apparatus having such a configuration, as shown in FIG. 1, a second paper storage in which a cooling paper B for cooling the intermediate transfer belt 55 is placed below the paper feed cassette 70. A paper feed tray 80 as a unit and a tray-side paper feed roller 81 for feeding the cooling paper B from the paper feed tray 80 are installed.

  The paper feed tray 80 is configured to be detachable from the main body portion of the image forming apparatus in the same manner as the paper feed cassette 70 in order to replenish or replace the cooling paper B. Further, as shown in FIG. 1, the tray-side paper feed roller 81 is disposed so as to contact the cooling paper B positioned on the lowermost side among the cooling papers B placed on the paper feeding tray 80. The cooling paper B placed on the paper feed tray 80 is fed by the tray-side paper feed roller 81 in order from the one located on the lower side, and is conveyed toward the first conveyance roller 72.

  The cooling paper B may be made of any material as long as it can absorb the heat of the intermediate transfer belt 55 when passing through the nip portion between the driving roller 56 and the secondary transfer roller 57. Larger ones absorb more heat. For example, the cooling paper B may be the same type as the recording paper stored in the paper feed cassette 70, or may be a thick paper dedicated to cooling. Further, the cooling paper B may have an image printed on at least one side thereof, or may not have an image printed on both sides. When an image is printed on at least one surface of the cooling paper B, that is, when the cooling paper B is a backing paper, a portion where the toner 53a is attached is more than a portion where the toner 53a is not attached. Absorbs heat. For this reason, the cooling paper B on which an image is printed on at least one side exhibits a higher cooling effect than the cooling paper B on which no image is printed on both sides.

  Further, as shown in FIG. 1, the image forming apparatus is installed between the nip portion between the driving roller 56 and the secondary transfer roller 57 and the fixing unit 60 in the conveyance route of the recording paper A, and the nip Passing through the second switching guide 82, which is a switching member for switching the conveyance direction of the cooling paper B in order to prevent the cooling paper B that has passed through the section from being conveyed toward the fixing unit 60, and the second switching guide 82 Installed on the upstream side of the first conveyance roller 72 in the conveyance route of the recording paper A and the third conveyance roller 83 that conveys the cooled cooling paper B toward the second conveyance roller 77, and passes through the plurality of second conveyance rollers 77. A third switching guide 84 is provided for switching the conveyance direction of the cooling paper B in order to prevent the cooled cooling paper B from being conveyed toward the first conveyance roller 72.

  Then, the cooling paper B that has passed the installation position of the third switching guide 84 is transported to the paper feed tray 80 through the transport route indicated by the dashed arrow in FIG. The cooling paper B is placed on top of the cooling paper B positioned on the uppermost side.

  Further, as shown in FIG. 2, the image forming apparatus includes a charging unit 51, an exposure unit 52, a developing unit 53, a fixing unit 60, and a primary transfer of each of the image forming units 10, 20, 30, and 40. A power supply unit 90 for supplying power to various rollers such as a roller 54, a driving roller 56, a secondary transfer roller 57, and a registration roller 73 and a motor (not shown) for rotating the photosensitive drum 50 is installed. A control unit 91 that controls the power supply unit 90, the above-described units and motors supplied with electric power from the power supply unit 90, and the first switching guide 76, the second switching guide 82, and the third switching guide 84. is set up. The control unit 91 includes a counter (not shown) that counts the number of continuous prints of the recording paper A in the single-sided printing mode or the double-sided printing mode.

  When printing on the recording sheet A using the image forming apparatus having such a configuration, the recording sheet A is heated by the fixing roller 61 when passing through the fixing unit 60 during continuous printing of the recording sheet A in the single-sided printing mode or the double-sided printing mode. Due to the heat radiation of the recording paper A, the temperature inside the apparatus rises, and the developing unit 53 and the like are heated accordingly. Further, during continuous printing of the recording paper A in the duplex printing mode, the recording paper A heated by the fixing roller 61 and the intermediate transfer belt 55 come into contact with each other at the nip portion between the driving roller 56 and the secondary transfer roller 57. The intermediate transfer belt 55 is heated, and the photosensitive drum 50 in pressure contact with the intermediate transfer belt 55 is heated. The temperatures of the photosensitive drum 50, the developing unit 53, and the intermediate transfer belt 55 increase as the number of continuous prints of recording paper increases.

  When the photosensitive drum 50, the developing unit 53, and the intermediate transfer belt 55 are heated to a predetermined temperature or more in this way, the properties of the toner 53a accommodated in the developing unit 53 are changed, so that printing is performed on recording paper. As the image quality deteriorates, the properties of the toner 53a adhering to the surface of the photosensitive drum 50 and the intermediate transfer belt 55 change, and thereby the quality of the image transferred from the intermediate transfer belt 55 to the recording paper decreases.

  Therefore, in addition to the single-sided printing mode and the double-sided printing mode described above, this image forming apparatus passes the cooling paper B fed from the paper feed tray 80 through the nip portion between the driving roller 56 and the secondary transfer roller 57. In this way, the intermediate transfer belt 55 that contacts the cooling paper B is cooled, and the photosensitive drum 50 that is in pressure contact with the intermediate transfer belt 55 and the developing unit 53 that is installed near the photosensitive drum 50 are cooled. Yes.

  Then, based on the measurement value of the counter provided in the control unit 91, when the control unit 91 confirms that the counter value has reached a predetermined value, the printing operation of the recording sheet A is temporarily stopped, Transition from duplex printing mode to cooling mode. For example, when images are continuously printed on 100 sheets of recording paper A, every time 10 sheets of recording paper A are printed, that is, every time the counter value reaches a multiple of 10, single-sided printing mode or duplex printing is performed. Transition from print mode to cooling mode. Then, one or more predetermined cooling sheets B are fed from the sheet feeding tray 80 and conveyed to the nip portion between the driving roller 56 and the secondary transfer roller 57. When the cooling operation in the cooling mode is completed, the printing operation of the recording paper A in the interrupted single-sided printing mode or double-sided printing mode is resumed.

  A timer (not shown) for measuring the elapsed time from the start of continuous printing of the recording paper A is installed in this image forming apparatus instead of the counter for counting the continuous printing number of the recording paper A. Also good. At this time, the time from when the continuous printing of the recording paper A is started until the counter value reaches a predetermined value is measured in advance, and this time is stored as the predetermined value. When the control unit 91 confirms that the timer value has reached a predetermined value, the printing operation of the recording paper A is temporarily stopped, and the single-sided printing mode or the double-sided printing mode is shifted to the cooling mode.

  In the image forming apparatus configured as described above, when the user gives an instruction to start a printing operation, power is supplied from the power supply unit 90 to each unit in the image forming apparatus and is output from the control unit 91. The operation of each unit in the image forming apparatus is controlled based on the control signal. Therefore, in the image forming apparatus shown in FIG. 1, the charging process, the exposure process, the developing process, the primary transfer process, the secondary transfer process, and the fixing process are sequentially performed.

  In the image forming apparatus shown in FIG. 1, the one-dot chain line arrow represents the conveyance route common to the recording paper A and the cooling paper B, the solid line arrow represents the conveyance route for the recording paper A, and the broken arrow represents the cooling paper. Each of the transport routes of B is represented. In the following description, the single-sided printing mode, the double-sided printing mode, and the cooling mode will be described in this order.

  First, when the printing operation of the recording paper A is performed in the single-sided printing mode, as shown in FIG. 3, the first switching guide 76 is switched in the direction indicated by the broken line in FIG. The two switching guides 82 are switched in the direction indicated by the broken line in FIG. Further, the third switching guide 84 is not operated because the first switching guide 76 is switched in the direction indicated by the broken line in FIG. 1 to prevent the recording paper A from being conveyed to the plurality of second conveying rollers 77. However, in order to secure the conveyance route of the cooling paper B in the cooling mode, it may be switched in advance to the direction indicated by the solid line in FIG.

  Then, after the operation of the first switching guide 76 and the second switching guide 82 by the control unit 91, the recording paper A fed from the paper feeding cassette 70 by the cassette side paper feeding roller 71 is shown by a solid line in FIG. It is conveyed to the 1st conveyance roller 72 through the conveyance route shown by the arrow. Then, after the recording paper A that has passed through the first transport roller 72 passes through the transport route indicated by the one-dot chain line arrow in FIG. 1, the orientation of the pair of registration rollers 73 is corrected and the transport timing is adjusted. It is conveyed toward the nip portion between the drive roller 56 and the secondary transfer roller 57.

  Thus, when the recording paper A is conveyed toward the nip portion between the drive roller 56 and the secondary transfer roller 57, the cyan image forming unit 10, the magenta image forming unit 20, the yellow image forming unit 30, and the black image In each of the forming units 40, first, the charging unit 51 uniformly charges the surface of the photosensitive drum 50 by discharging the charging wire 51a in the charging process. Next, the exposure unit 52 of each of the image forming units 10, 20, 30, 40 irradiates a laser beam from a semiconductor laser (not shown) toward the photosensitive drum 50 in the exposure process, and the surface of the photosensitive drum 50 is exposed. Among them, an electrostatic latent image is formed in the portion scanned with the laser beam.

  The developing units 53 of the image forming units 10, 20, 30, and 40 supply the toner 53 a charged in the developing process to the photosensitive drum 50 by the developing roller 53 b, thereby forming electrostatic charges formed on the surface of the photosensitive drum 50. Development is performed by attaching the toner 53a to the latent image. Subsequently, in the primary transfer step, the image formed on the surface of the photosensitive drum 50 of each image forming unit 10, 20, 30, 40 is transferred to the intermediate transfer belt 55 driven at a predetermined speed. At this time, the image formed on the surface of the photosensitive drum 50 of each of the image forming units 10, 20, 30, and 40 is transferred and superimposed on the surface of the intermediate transfer belt 55 at a predetermined timing. An image composed of a plurality of colors is formed.

  Thereafter, in the secondary transfer step, the image formed on the surface of the intermediate transfer belt 55 is transferred to the recording paper A that passes through the nip portion between the driving roller 56 and the secondary transfer roller 57. Then, the recording sheet A on which the image has been transferred in the secondary transfer step passes through the installation position of the second switching guide 82, and then passes through the conveyance route indicated by the solid line arrow in FIG. And the pressure roller 63 are conveyed to the nip portion.

  In addition, by sending a control signal for turning on the fixing heater 62 from the control unit 91 to the power supply unit 90, power supply from the power supply unit 90 to the fixing heater 62 is started, and the fixing heater 62 is heated. The fixing roller 61 is heated to a temperature at which the toner 53a can be stably fixed onto the recording paper A by the fixing heater 62. Then, the fixing unit 60 melts the toner 53a of the recording sheet A passing through the nip portion between the fixing roller 61 and the pressure roller 63 in the fixing unit 60 by the heat of the fixing roller 61 and the pressure roller 63 in the fixing process. Thus, the toner 53a is fixed to the recording paper A by applying pressure to the recording paper A.

  Thereafter, the recording paper A on which the toner 53a has been fixed in the fixing step passes through the conveyance route indicated by the solid arrow in FIG. 1 and passes through the installation position of the first switching guide 76, and then is discharged by the paper discharge roller 74 of the image forming apparatus. It is fed into the cylinder and discharged to the in-cylinder discharge tray 75.

  Next, when the printing operation of the recording paper A is performed in the duplex printing mode, as shown in FIG. 3, the second switching guide 82 is switched in the direction indicated by the broken line in FIG. The 3rd switching guide 84 switches to the direction shown with a broken line in FIG. Further, as shown in FIG. 3, the first switching guide 76 is switched in the direction indicated by the solid line in FIG. 1 when an image is printed on the first surface of the recording paper A, and the second surface of the recording paper A. When an image is printed, the direction is switched to a direction indicated by a broken line in FIG.

  Then, after the first to third switching guides 76, 82, 84 are operated by the control unit 91, the recording paper A fed from the paper feed cassette 70 by the cassette side paper feed roller 71 is shown by a solid line in FIG. It is conveyed to the 1st conveyance roller 72 through the conveyance route shown by the arrow of. Subsequently, the recording sheet A that has passed through the first transport roller 72 is transported to the pair of registration rollers 73 through a transport route indicated by a one-dot chain line arrow in FIG. 1, and between the drive roller 56 and the secondary transfer roller 57. The image is transferred to the first surface when passing through the nip portion. The recording sheet A having the image transferred onto the first surface passes through the installation position of the second switching guide 82, and then passes through the conveyance route indicated by the solid line arrow in FIG. The toner 53a is fixed to the first surface when it is conveyed toward the nip portion between the rollers 63 and passes through the nip portion.

  The recording paper A on which the first surface that has passed through the fixing unit 60 is printed is conveyed toward the paper discharge roller 74, and the paper discharge roller when the rear end portion of the recording paper A reaches the position of the paper discharge roller 74. The rotation of 74 is reversed. Thus, the recording sheet A on which the first surface is printed is conveyed toward the second conveyance roller 77 through the first switching guide 76. When the rear end portion of the recording paper A reaches the position of the paper discharge roller 74, the portion from the portion sandwiched between the paper discharge rollers 74 to the front end portion of the recording paper A is exposed outside the apparatus.

  Subsequently, the recording paper A on which the image is printed on the first surface is conveyed by a plurality of second conveying rollers 77, so that a recording route indicated by a solid line arrow in FIG. 1 and a one-dot chain line arrow in FIG. Pass the indicated transport route. Then, after the recording paper A having the image printed on the first surface passes through the installation position of the third switching guide 84, the recording paper A is conveyed to the first conveyance roller 72 through the conveyance route indicated by the solid line arrow in FIG. Is done. After that, the recording paper A on which the image is printed on the second surface by performing the same printing operation as when the image is printed on the first surface is sent out into the cylinder of the image forming apparatus by the paper discharge roller 74. Then, it is discharged to the in-body discharge tray 75.

  Here, as described above, when continuous printing of the recording paper A is performed in the single-sided printing mode or the double-sided printing mode, the number of continuous printing sheets of the recording paper A is counted by the counter provided in the control unit 91. When the control unit 91 confirms that the count value of the counter has reached a predetermined value, the printing operation of the recording paper A is temporarily stopped, and the mode is shifted from the single-sided printing mode or the double-sided printing mode to the cooling mode. Below, the conveyance route of the cooling paper B in this cooling mode is demonstrated in detail.

  When the control unit 91 confirms that the count value of the counter has reached a predetermined value, the recording paper A on which an image is printed at this time is discharged to the in-body discharge tray 75, and then the single-sided printing mode Or it shifts from the duplex printing mode to the cooling mode. Then, as shown in FIG. 3, the second switching guide 82 is switched in the direction indicated by the solid line in FIG. 1 and the third switching guide 84 is switched in the direction indicated by the solid line in FIG. . The first switching guide 76 is not operated because the second switching guide 82 is switched in the direction indicated by the solid line in FIG. 1 to prevent the recording paper A from being conveyed to the fixing unit 60. In order to secure the transport route of the recording paper A when the operation is resumed, the recording paper A is held in the direction indicated by the broken line in FIG. 1 in the single-sided printing mode, and switched in advance to the direction indicated by the solid line in FIG. May be.

  Then, after the operation of the second switching guide 82 and the third switching guide 84 by the control unit 91, the cooling paper B fed from the paper feed tray 80 by the tray side paper feed roller 81 is indicated by a broken line in FIG. It is conveyed to the 1st conveyance roller 72 through the conveyance route shown by the arrow. Subsequently, after the recording paper A that has passed through the first conveyance roller 72 passes through a conveyance route indicated by a one-dot chain line arrow in FIG. 1, the orientation of the recording sheet A is corrected and the conveyance timing is adjusted in the pair of registration rollers 73. Then, it is conveyed toward the nip portion between the driving roller 56 and the secondary transfer roller 57.

  Here, when the mode is shifted from the single-sided printing mode or the double-sided printing mode to the cooling mode, the temperature near the place where the paper feed tray 80 is installed in the image forming apparatus is the temperature near the place where the fixing unit 60 is installed. Is lower than. For this reason, an air flow from the paper feed tray 80 to the fixing unit 60, that is, an air flow from the lower side to the upper side is generated by natural convection inside the image forming apparatus. Since the cold air near the installation surface of the image forming apparatus is taken into the apparatus through the gap provided in the image forming apparatus, the cooling paper B placed on the paper feed tray 80 is always in contact with the air. It is cooled.

  Therefore, the cooling paper B conveyed to the nip portion between the driving roller 56 and the secondary transfer roller 57 absorbs heat from the intermediate transfer belt 55 in contact with the cooling paper B when passing through the nip portion. The intermediate transfer belt 55 is cooled, and the photosensitive drum 50 in pressure contact with the intermediate transfer belt 55 and the developing unit 53 installed in the vicinity of the photosensitive drum 50 are cooled. The cooling paper B that has passed through the nip portion between the driving roller 56 and the secondary transfer roller 57 passes through the installation position of the second switching guide 82, and passes through the conveyance route indicated by the dashed arrow in FIG. It is conveyed to the roller 83. The cooling paper B that has passed through the third transport roller 83 is transported to the second transport roller 77 through a transport route indicated by a one-dot chain line arrow in FIG. 1, and then passes the installation position of the third switching guide 84. 1 is stacked on the cooling paper B positioned on the uppermost side among the cooling papers B placed on the paper feed tray 80 through the conveyance route indicated by the dashed arrow in FIG.

  In the cooling mode, when a plurality of sheets of cooling paper B are fed from the paper feed tray 80, each of the plurality of sheets of cooling paper B passes through the nip portion between the drive roller 56 and the secondary transfer roller 57. As a result, the intermediate transfer belt 55 is cooled, and the photosensitive drum 50 in pressure contact with the intermediate transfer belt 55 and the developing unit 53 installed in the vicinity of the photosensitive drum 50 are cooled.

  In this embodiment, when images are continuously printed on recording paper, the control unit 91 confirms that the count value by the counter has reached a predetermined value after the printing operation in the single-sided printing mode or the double-sided printing mode is started. Then, the printing operation is temporarily stopped to shift from the single-sided printing mode or the double-sided printing mode to the cooling mode, and the heat of the intermediate transfer belt 55 is absorbed by the paper fed from the paper feed tray 80, and this intermediate transfer belt 55 To cool down. Therefore, according to the present embodiment, it is possible to reliably prevent the image quality from being deteriorated due to the influence of the heat of the intermediate transfer belt 55 without complicating the configuration of the apparatus.

  Further, according to the present embodiment, the photosensitive drum 50 pressed against the intermediate transfer belt 55 is cooled by cooling the intermediate transfer belt 55, and the developing unit 53 installed in the vicinity of the photosensitive drum 50 is also cooled. Therefore, it is possible to reliably prevent the image quality from deteriorating due to the temperature rise inside the apparatus.

  Further, in the present embodiment, the end of the cooling paper B is absorbed while the cooling paper B whose temperature has increased by absorbing the heat of the intermediate transfer belt 55 is conveyed by the first to third conveyance rollers 76, 82, and 84. The part may be deformed due to curling or the like. However, the cooling paper B placed on the paper feed tray 80 is fed from the paper feed tray 80 and when it is returned to the paper feed tray 80 after being transported inside the apparatus. The direction is reversed. Therefore, even if the end portion of the cooling paper B is deformed while being transported inside the image forming apparatus, the cooling paper B is next fed from the paper feed tray 80 and transported inside the image forming apparatus. Sometimes, a force is applied in the direction opposite to the deformed direction, so that the deformation of the cooling paper B can be corrected.

  In the image forming apparatus, the recording paper is fed from the paper feeding cassette 70 and the cooling paper is fed from the paper feeding tray 80. However, only the paper feeding cassette 70 is installed in the image forming apparatus. May be. In the cooling mode, in order to discharge the recording paper fed from the paper feeding cassette 70 and passing through the nip portion between the driving roller 56 and the secondary transfer roller 57 to the in-body paper discharge tray 75, the first The switching guide 76 is switched in the direction indicated by the broken line in FIG. 1, and the second switching guide 82 is switched in the direction indicated by the broken line in FIG. As a result, even in an image forming apparatus capable of single-sided printing, the intermediate transfer belt 55, the photosensitive drum 50, the developing unit 53, and the like can be cooled using the recording paper stored in the paper feed cassette 70.

  In the image forming apparatus, when the same number of sheets are continuously printed in the single-sided printing mode and the double-sided printing mode, the temperature in the apparatus is higher in the double-sided printing mode than in the single-sided printing mode. This is because the recording sheet A on which the first surface that has passed through the fixing unit 60 is printed passes through the fixing unit 60 in the single-sided printing mode in which the recording sheet A passes through the discharge rollers 74 and is discharged to the in-body discharge tray 75. In the double-sided printing mode in which the recording sheet A is conveyed through the inside of the image forming apparatus in order to print the second side of the recording sheet A on which one side is printed, the recording sheet A on which the first side is printed. This is because the transport route becomes long and the heat radiation amount of the recording paper A increases. Therefore, the cooling paper B that passes through the nip portion between the drive roller 56 and the secondary transfer roller 57 in the cooling mode when the mode is shifted from the single-sided printing mode to the cooling mode and when the mode is shifted from the double-sided printing mode to the cooling mode. By changing the number of sheets, the intermediate transfer belt 55, the photosensitive drum 50, the developing unit 53, and the like can be cooled more effectively.

  In the image forming apparatus, the conveyance speed of the recording paper A in the single-sided printing mode or the double-sided printing mode and the conveyance speed of the cooling paper B in the cooling mode may be changed. This can be realized by changing the amount of current supplied to a motor (not shown) that rotates the driving roller 56 and the second transfer roller 57. Then, the nip between the driving roller 56 and the secondary transfer roller 57 causes the cooling paper B to be lower than the conveyance speed of the recording paper A in the single-sided printing mode or the double-sided printing mode. It is possible to lengthen the time of contact with the portion, and the cooling paper B can further cool the intermediate transfer belt 55, the photosensitive drum 50, the developing unit 53, and the like.

  In the image forming apparatus, the recording paper A contained in the paper feed cassette 70 is used for printing an image, and the cooling paper B placed on the paper feed tray 80 is used as the driving roller 56 and the secondary paper. Although the transfer roller 57 is used for cooling, the present invention is not limited to this. That is, when a plurality of recording sheets A are placed as the cooling sheets B on the sheet feeding tray 80, the recording sheets A of the number that can be cooled are left on the sheet feeding tray 80, and other recording sheets A are imaged. It may be used for printing. The number of recording sheets A placed on the sheet feeding tray 80 can be detected using a sensor or the like. Thereby, recording paper A of different sizes can be stored in the paper feed cassette 70 and the paper feed tray 80, and the usability of the image forming apparatus can be improved.

  In the image forming apparatus, the amount of current supplied from the power supply unit 90 to the fixing roller 61 is set so that the temperature of the fixing roller 61 during the printing operation is substantially constant. For this reason, the amount of current supplied from the power supply unit 90 to the fixing roller 61 is greater when the temperature inside the machine is lower than when the temperature inside the machine is high. The temperature inside the machine changes according to the temperature outside the machine. Therefore, the amount of current supplied from the power supply unit 90 to the fixing roller 61 is measured to estimate the temperature in the apparatus, and the cooling paper B passing through the nip portion between the driving roller 56 and the secondary transfer roller 57 in the cooling mode is estimated. By changing the number of sheets, it is possible to cool the intermediate transfer belt 55, the photosensitive drum 50, the developing unit 53, and the like more effectively according to changes in the outside air temperature of the day and changes in season. It becomes.

  In the image forming apparatus, the cooling paper B placed on the paper feed tray 80 is cooled by the outside air taken into the apparatus through the gap provided in the image forming apparatus. When the gap provided in the apparatus is narrow and the amount of outside air taken into the machine is small, a fan (not shown) is attached in the vicinity of the paper feed tray 80 to forcibly take outside air into the machine. It may be.

  In addition, the configuration of the present invention is applied to an image forming apparatus having both a single-sided printing mode and a double-sided printing mode. The present invention may be applied to other image forming apparatuses.

  Further, the configuration of the present invention is applied to the image forming apparatus including the tandem developing unit 53. However, the present invention is not limited thereto, and the configuration of the present invention is applied to the image forming apparatus including the rotary developing unit. It is good.

  As described above, the present invention is useful for image forming apparatuses such as copying machines and printers.

1 is a diagram illustrating a structure of an image forming apparatus according to an embodiment. 1 is a block diagram illustrating a partial configuration of an image forming apparatus according to an embodiment. It is a figure which shows the state of the 1st-3rd switching guide in each mode of single-sided printing mode, double-sided printing mode, and cooling mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cyan image forming unit 20 Magenta image forming unit 30 Yellow image forming unit 40 Black image forming unit 50 Photosensitive drum 51 Charging unit 52 Exposure unit 53 Developing unit 54 Primary transfer roller 55 Intermediate transfer belt 56 Drive roller 57 Secondary transfer roller 60 Fixing unit 70 Paper feed cassette 71 Cassette side paper feed roller 72 First transport roller 73 Registration roller 74 Paper discharge roller 75 In-body paper discharge tray 76 First switching guide 77 Second transport roller 80 Paper feed tray 81 Tray side paper feed roller 82 Second switching guide 83 Third transport roller 84 Third switching guide

Claims (7)

In an image forming apparatus that includes a sheet storage unit that can store a large number of sheets, and that prints an image on a sheet fed from the sheet storage unit.
A printing mode for printing an image on a sheet fed from the sheet storage unit, and a cooling for cooling the member by absorbing heat of the member that transfers the image to the sheet fed from the sheet storage unit. Mode, and
When continuously printing images on paper, the printing operation is temporarily stopped when a predetermined timing is reached after the printing operation in the printing mode is started, and the cooling mode is shifted from the printing mode. An image forming apparatus, wherein the sheet fed from the sheet storage unit returns from the cooling mode to the printing mode after passing through the installation position of the member. Equipped with a counter that counts the number of continuous prints of paper,
The image forming apparatus according to claim 1, wherein the predetermined timing is determined based on a continuous print number of sheets counted by the counter. With a timer that measures the continuous printing time of paper,
The image forming apparatus according to claim 1, wherein the predetermined timing is determined based on a continuous printing time of the paper measured by the timer. A fixing unit that fixes an image on a sheet onto which an image that has passed through the installation position of the member is transferred in the printing mode; and a switching member that switches a conveyance direction of the sheet that has passed through the installation position of the member.
The switching member switches the transport direction of the paper that has passed through the installation position of the member between the printing mode and the cooling mode, so that the paper that has passed through the installation position of the member in the cooling mode is transferred to the fixing unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is prevented from being conveyed. The paper storage unit is constituted by a first paper storage unit and a second paper storage unit,
5. The image formation according to claim 4, wherein the sheet is fed from the first sheet storage unit in the printing mode and the sheet is fed from the second sheet storage unit in the cooling mode. apparatus.   The sheet having passed through the installation position of the member in the cooling mode is conveyed to the second sheet storage unit, stored in the second sheet storage unit, and fed again. The image forming apparatus according to 5. The printing mode is composed of a single-sided printing mode for printing only one side of the paper and a double-sided printing mode for printing on both sides of the paper,
The image forming apparatus according to claim 1, wherein the predetermined timing is different between the single-sided printing mode and the double-sided printing mode.

Images