JP2010096952A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is constituted so that a sheet stacking part may not be a hindrance, which suppresses heat of a fixing part, which achieves reduction of power consumption, and which can use each kind of sheet such as a sheet having high stiffness, while achieving miniaturization of the apparatus. <P>SOLUTION: A sheet stacking tray 14 is arranged to be exposed on the upper part of a printer body 50A. A cassette 15, a process cartridge G functioning as an image forming part and a fixing device 6 are successively arranged under the sheet stacking tray 14. A lead-in path B is arranged on the side of the fixing device 6. A toner image is formed on a sheet P by the image forming part. The sheet P on which the toner image has been formed is led in the lead-in path B after the toner image is fixed by the fixing device 6 once. Then, the sheet P is switched back, so that the toner image is fixed by the fixing device 6 again, and the sheet on which the toner image has been fixed is ejected to the sheet stacking tray 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to an image forming apparatus suitable for being stored in a desk.

  In recent years, digitization of documents has rapidly progressed due to digitization of information / IT in offices. As a result, opportunities for printing on sheets such as paper from PCs and digital terminals have also increased dramatically. In addition, by this, the number of businesses that conduct business in small offices and homes using information communication devices such as PCs called SOHO (Small Office / Home Office) is increasing. Further, further downsizing / space-saving is desired for PCs and peripheral devices thereof, and this demand is high in image forming apparatuses such as printers. In addition, in the office, the power for operating various devices has increased dramatically compared to the conventional office, and there is a strong demand for power saving of the devices.

  Therefore, in order to save space, an image forming apparatus housed in a desk such as a desk having a cabinet (sleeves) or a side desk has been proposed (see Patent Documents 1 to 3), which does not require a dedicated stand and is simple. Operability is realized. In this type of image forming apparatus, the sheet on which the image has been formed is discharged to a sheet stacking portion protruding from one side surface of the apparatus main body. A sheet storage unit that stores a sheet can be pulled out from one side surface of the apparatus main body. As described above, the sheet stacking unit and the sheet storage unit are arranged on one side surface of the apparatus main body to improve usability. Accordingly, the sheet conveyance path extending from the sheet storage unit to the sheet stacking unit is configured by a U-turn path that makes a U-turn from the sheet storage unit and a horizontal path that extends horizontally from the U path, and the image forming unit and the fixing unit are sequentially arranged in the horizontal path. I try to arrange it.

JP-A-61-80267 JP 61-80268 A Japanese Patent Laid-Open No. 5-308476

  However, in the conventional image forming apparatus, since the sheet stacking portion protrudes from the side surface of the desk, it is large and unpleasant, and the user hits the sheet stacking portion, and the sheet falls from the sheet stacking portion and becomes dirty. There is a risk of it.

  Furthermore, since the image forming apparatus is housed in a closed desk instead of an open space, a fan, a duct, etc. for exhausting heat are used to prevent heat generated in the fixing unit from being trapped in the desk. It was necessary to provide a heat exhausting means. In the case where the exhaust heat means is provided in this way, it is difficult to avoid an increase in cost and an increase in power consumption.

  Furthermore, since the image forming apparatus is stored on a desk, it is necessary to reduce the size of the apparatus main body. Therefore, if the apparatus main body is simply downsized, the radius of curvature of the U-turn path of the sheet conveyance path becomes small, making it difficult to use a highly rigid sheet such as cardboard, and the usable sheets are limited. There was a problem that.

  Therefore, the present invention is not limited to the sheet stacking unit, can suppress the heat of the fixing unit, can reduce the power consumption, and reduce the size of the apparatus, and various sheets such as a highly rigid sheet. It is an object of the present invention to provide an image forming apparatus that can use the above-described image forming apparatus.

  In order to achieve the above object, in an image forming apparatus comprising an image forming unit for forming a toner image on a sheet, fixing the toner image formed on the sheet by the image forming unit, and discharging the sheet from the apparatus main body. A sheet stacking unit that is disposed at an upper portion of the apparatus main body and stacks sheets discharged from the apparatus main body; and a sheet storage unit that is disposed between the sheet stacking unit and the image forming unit and stores sheets. A fixing unit disposed below the image forming unit and configured to fix the toner image formed on the sheet by the image forming unit; and a sheet disposed on a side of the fixing unit and having the toner image fixed by the fixing unit. A retraction path that is pulled in to switch back, conveys the sheet stored in the sheet storage unit downward, and forms a toner image on the sheet by the image forming unit. Then, after the toner image is fixed on the sheet on which the toner image is formed by the fixing unit and pulled into the drawing path, the toner image is fixed on the fixing unit again by switching back. The fixed sheet is conveyed upward and discharged to the sheet stacking unit.

  According to the present invention, since the sheet stacking unit is disposed on the upper portion of the apparatus main body, the sheet stacking unit does not get in the way, and the user can avoid hitting the sheet stacking unit and prevent the sheet from falling. In addition, the device becomes smaller and looks better.

  Furthermore, since the toner image formed on the sheet is fixed twice by the fixing unit, the fixing temperature of the fixing unit can be lowered and the power consumption can be reduced. And since the fixing temperature of a fixing part can be lowered | hung, it can suppress that a heat | fever accumulates in a desk, without providing a separate heat exhaust means.

  Further, since the toner image of the sheet is fixed twice by the fixing unit and the sheet is discharged to the sheet stacking unit disposed at the upper part of the apparatus main body, the sheet storage unit, the image forming unit, and the fixing unit are disposed below the sheet stacking unit. By sequentially arranging these, the capacity of each part in the apparatus main body is improved. Thereby, the apparatus can be reduced in size.

  Then, the sheet conveyed downward from the sheet storage unit is first fixed in the fixing unit through the image forming unit, and after being drawn into a drawing passage disposed on the side of the fixing unit, the sheet is switched back. Second fixing is performed by the fixing unit, and the sheet is conveyed upward and discharged to the sheet stacking unit. Therefore, since the sheet does not pass through the U-turn path having a small curvature radius, the sheet is not excessively stressed even if the apparatus is downsized. As described above, the sheet is not excessively stressed while downsizing the apparatus, and various sheets including a highly rigid sheet can be used.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of a laser beam printer as an example of an image forming apparatus according to the present embodiment. FIG. 2 is an explanatory view showing a state in which the laser beam printer is housed on the desk.

  1 and 2, reference numeral 50 denotes a laser beam printer (hereinafter referred to as “printer”) as an image forming apparatus, and reference numeral 50A denotes a printer main body as an apparatus main body. In FIG. 2, the printer main body 50 </ b> A is configured to be housed in the cabinet 201 among the cabinets 200 and 201 provided on both sides of the desk 100. The desk 100 is provided with a connector 130 such as USB / IEEE1394 for connecting an electronic device such as a PC and the printer 50. Thereby, connection of electronic devices, such as PC, is easy. Note that although a wired connection example is shown in this embodiment mode, wireless equipment may be installed.

  As shown in FIG. 1, the printer 50 includes a process cartridge (hereinafter referred to as “cartridge”) G as an image forming unit that forms a toner image on a sheet P. The cartridge G includes a photosensitive drum 1 as an image carrier that is rotatably supported, a charging roller 2, a developing roller 4 as a developing device, and a cleaning device 7, and these are integrally formed with a case 10. It is stored in. The cartridge G is detachably supported with respect to the printer main body 50A. The case 10 of the cartridge G is composed of an upper case half 10a and a lower case half 10b.

  The photosensitive drum 1 is rotationally driven at a predetermined process speed in the direction of arrow R1 by a driving means (not shown).

  The printer 50 includes a transfer roller 5 that is disposed in pressure contact with the photosensitive drum 1 of the cartridge G, and a transfer nip portion T is formed by the photosensitive drum 1 and the transfer roller 5. The printer 50 includes an exposure device 3 as an exposure unit that exposes the surface of the photosensitive drum 1 and forms an electrostatic latent image on the surface.

  Further, the printer 50 includes a sheet feeding device 9 that feeds the sheet P, a pair of conveying rollers 8 that conveys the fed sheet P to the photosensitive drum 1 (that is, the transfer nip portion T) of the cartridge G, and It has. In addition, the printer 50 includes a fixing device 6 as a fixing unit that thermally fixes a toner image formed on the sheet P, and a sheet stacking tray as a sheet stacking unit on which the fixed sheets P discharged from the printer main body 50A are stacked. 14.

  The fixing device 6 includes a heater unit 25 and a pressure roller 26 biased by a compression spring or a tension spring (not shown). A gear or pulley for driving transmission is provided at an end of the pressure roller 26. And the pressure roller 26 is rotated to convey the sheet P. In addition, a motor (not shown) is connected to the pressure roller 26. The pressure roller 26 of the fixing device 6 controls the sheet conveyance direction in the forward direction and the reverse direction by forward and reverse rotation of the motor. As a result, the fixing device 6 can transport the sheet P in the forward direction, and can transport the sheet P in the reverse direction by switching back.

  The sheet feeding device 9 includes a cassette 15 as a sheet storage unit that stores sheets P. The cassette 15 is disposed substantially horizontally, and an opening 15 a for feeding the sheet P is formed at a portion corresponding to the leading end of the sheet P at the lower part of the cassette 15. Further, the sheet feeding device 9 is disposed in the vicinity of the opening 15 a of the cassette 15, has a half-moon shaped feeding roller 11 for feeding the sheet P, and the lowermost sheet stored in the cassette 15. P is fed at a predetermined timing. Further, the sheet feeding device 9 is provided in a direction opposite to the feed roller 16 through a feed roller 16 that transports the sheet P fed from the feed roller 11 to the pair of transport rollers 8 and a torque limiter (not shown). And a retard roller 17 to which a torque of 5 is applied. The retard roller 17 is rotatably supported by a predetermined pressure applied to the feed roller 16, and one sheet P is fed even when a plurality of sheets are fed by the reverse rotation torque of the retard roller 17. It can be separated and conveyed one by one. Here, instead of the retard roller 17, a separation pad for applying a pad member of a high friction member such as rubber or elastomer to the feed roller 16 with a predetermined pressure may be provided.

  The printer 50 includes a control device 39 having a CPU that controls the entire printer 50. The control device 39 operates each actuator when print data is transmitted from a PC or a similar print instruction device wired or wirelessly connected to the printer main body 50A.

  By the way, in the present embodiment, the sheet stacking tray 14 is disposed on the upper part of the printer main body 50A, and is disposed so that the sheet stacking surface is exposed to the outside of the printer main body 50A. As shown in FIG. 2, when the printer main body 50A is stored in the cabinet 201 of the desk 100, the sheet stacking tray 14 is exposed on the desk. By disposing the sheet stacking tray 14 in this way, the sheet stacking tray 14 does not protrude to the side of the printer main body 50 </ b> A, so that it does not get in the way and the user can avoid hitting the sheet stacking tray 14. Accordingly, the sheet P can be prevented from dropping, and the printer 50 can be reduced in size and look good.

  Next, as shown in FIG. 2, since the printer 50 is incorporated in the desk 100, the heat generated in the printer main body 50A tends to be trapped. The most heat generating source in the printer 50 is the fixing device 6. That is, if the fixing temperature in the fixing device 6 is lowered, it is possible to suppress heat from being accumulated inside the printer main body 50A.

  Therefore, in the present embodiment, the fixing temperature of the fixing device 6 is set to a temperature lower than the case where the toner image is fixed once, and the toner image formed on the sheet P is fixed twice by the fixing device 6. The sheet stacking tray 14 is configured to discharge the sheet.

  More specifically, first, the cassette 15 is disposed immediately below (below) the sheet stacking tray 14 disposed on the upper portion of the printer main body 50A. The cassette 15 is housed in the printer main body 50A and is supported so as to be pulled out. A handle 103 is attached to one side surface of the cassette 15 and can be slid sideways from the printer main body 50 </ b> A when the user grasps and pulls the handle 103. The cassette 15 has no portion protruding from the side surface of the printer main body 50A, and is accommodated in the printer main body 50A so as to be compact.

  A cartridge G is disposed below the cassette 15. That is, the cassette 15 is disposed between the sheet stacking tray 14 and the cartridge G. A fixing device 6 is disposed below the cartridge G. Thus, the cassette 15, the cartridge G, and the fixing device 6 are sequentially arranged in the printer main body 50A downward.

  In other words, in the present embodiment, the toner image of the sheet P is fixed twice by the fixing device 6 and the sheet is discharged onto the sheet stacking tray 14 disposed on the upper portion of the printer main body 50A. With such a configuration, the cassette 15, the cartridge G, and the fixing device 6 are sequentially arranged below the sheet stacking tray 14, so that the capacity of each part in the printer main body 50 </ b> A is improved. Thereby, the apparatus can be reduced in size.

  The printer 50 is formed to extend downward from the cassette 15, and includes a main conveyance path A that guides the sheet P from the cassette 15 through the cartridge G to one side of the fixing device 6. The main conveyance path A is formed in a substantially C shape so as to convey the sheet P from the cassette 15 to the fixing device 6 without stress, and a cartridge G is disposed inside the main conveyance path A.

  Further, the printer 50 includes a pull-in passage B that is formed on the other side of the fixing device 6 so as to extend laterally (that is, in a substantially horizontal direction). The pull-in passage B is formed by a sheet guide 24 extending in a substantially horizontal direction. A space R is formed between the cassette 15 and the drawing passage B facing each other. In this space R, the exposure device 3 and the control device 39 are arranged, and each device is stored compactly in a narrow space, so that the storage property is improved and the device can be miniaturized.

  Further, the printer 50 is formed so as to extend upward from one side of the fixing device 6 substantially parallel to the main transport path A, and guides the sheet P that has passed through the fixing device 6 from the drawing path B to the sheet stacking tray 14. A discharge passage C is provided. The discharge path C is formed in a substantially C shape in the same direction as the main transport path A so as to transport the sheet P from the fixing device 6 to the sheet stacking tray 14 without stress. The discharge passage C is disposed outside the main transport passage A.

  Here, the main conveyance path A and the discharge path C are formed by a pair of guides. One guide of the main conveyance path A is constituted by a case 10 of the cartridge G. In addition, the other guide forming the main conveyance path A and the one guide forming the discharge path C are constituted by a guide member 20 configured integrally.

  A switching member 80 is rotatably provided at the lower end of the guide member 20, and a first position for guiding the sheet P to the fixing device 6 and a sheet from the fixing device 6 to the discharge passage C are guided. It is possible to switch to the second position.

  The other guide forming the discharge passage C is constituted by a guide member 21 constituting a side wall of the printer main body 50A, and a lower end thereof is rotatably supported by a shaft 21a. That is, the guide member 21 is supported so as to be rotatable about the shaft 21a, and the discharge passage C can be opened and closed by rotating the guide member 21.

  A sheet detection sensor S1 is provided between the conveyance roller pair 8 in the main conveyance path A and the photosensitive drum 1 of the cartridge G as an image forming unit. In addition, a sheet detection sensor S2 as a detection unit is provided in the vicinity of the entrance of one side of the fixing device 6 (the side where the sheet P that has passed through the photosensitive drum 1 of the cartridge G is introduced). In addition, a conveyance roller pair 18 and a discharge roller pair 13 are sequentially provided in the discharge passage C, and a sheet detection sensor S3 is provided in the vicinity of the discharge roller pair 13.

  The sheet detection sensors S1 and S3 have a lever and a photo interrupter (not shown), and can detect the leading edge of the sheet P when the leading edge of the sheet P hits the lever and swings. The sheet P may be directly irradiated with light, and the presence or absence of the reflected light may be observed to detect the passage of the sheet.

  The sheet detection sensor S2 detects the presence or absence of the sheet P, and the control device 39 performs switching control of the position of the switching member 80 and the conveyance direction of the fixing device 6 based on the detection result.

  A handle 131 is attached to one side surface of the printer main body 50A, and the user can hold the printer main body 50A by sliding it sideways from the desk 100.

  Next, the operation of the printer 50 will be described. FIG. 3 is an explanatory view showing a state in which the sheet P is being fed from the sheet feeding device 9, and FIG. 4 is an explanatory view showing the vicinity of the photosensitive drum 1 in FIG.

  When print data is transmitted from a PC or a similar print instruction device connected to the printer main body 50A by wire or wirelessly, each actuator starts operation by the control device 39 built in the printer main body 50A.

  The sheet P fed from the cassette 15 is conveyed by the conveyance roller pair 8 and the leading edge is detected by the sheet detection sensor S1. With the passage timing of the sheet detection sensor S1 as a trigger, an electrostatic latent image is formed on the photosensitive drum 1 by the exposure device 3 so that the leading edge of the image coincides with the leading edge of the sheet P. Then, the sheet P whose leading edge is detected by the sheet detection sensor S <b> 1 is conveyed by the conveyance roller pair 8 to the transfer nip portion T between the photosensitive drum 1 and the transfer roller 5.

  Here, in FIG. 4, L <b> 1 is a conveyance distance between the sheet detection sensor S <b> 1 and the transfer nip T, and L <b> 2 is the photosensitive drum 1 from the exposure position on the photosensitive drum 1 to the transfer nip T. This is the upper circumference. Then, assuming that the sheet conveying speed of the conveying roller pair 8 is V1, the peripheral speed of the outer periphery of the photosensitive drum 1 is V2, and the time when the sheet leading edge passes through the sheet detection sensor S1 is 0, the exposure start time t has the following relationship: It is obtained by the formula.

  FIG. 5 is an explanatory diagram showing the vicinity of the fixing device 6 performing the first fixing. FIG. 6 is an explanatory diagram showing the vicinity of the fixing device 6 performing the second fixing.

  Next, as shown in FIG. 5, the sheet P on which the toner image is formed by the photosensitive drum 1 passes through the switching member 80 that is rotated in the direction of the arrow D1 and switched to the first position, and the toner P It is guided to the fixing device 6 with the image forming surface on which the image is formed facing upward.

  At this time, the pressure roller 26 of the fixing device 6 rotates in the forward direction in the direction of the arrow R2, and fixes the toner image on the sheet P while sandwiching and transporting the sheet P in the forward direction. Thus, the sheet P on which the first toner image has been fixed is drawn into the drawing path B.

  When the trailing edge of the sheet P is detected by the sheet detection sensor S2, the rotation of the pressure roller 26 is temporarily stopped while the sheet P is held between the heater unit 25 and the pressure roller 26. Then, as shown in FIG. 6, the switching member 80 is rotated in the arrow D2 direction to move to the second position, and the pressure roller 26 is rotated in the reverse direction in the arrow R3 direction. As a result, the sheet P is switched back, and the toner image is fixed a second time while being conveyed in the reverse direction by the fixing device 6, and is guided to the discharge passage C. As described above, since the sheet P is switched back before the sheet P is detached from the fixing device 6, a pair of conveying rollers for conveying the sheet to the fixing device 6 is disposed in the drawing path B in order to fix the image again by the fixing device 6. There is no need to do.

  Then, the toner image is fixed again by the fixing device 6 and the sheet P guided to the discharge passage C is conveyed upward by the conveying roller pair 18 and is discharged from the printer main body 50A by the discharging roller pair 13. The sheets are stacked on the sheet stacking tray 14 with the image forming surface facing downward.

  As described above, when the sheet P fed from the cassette 15 passes through the main conveyance path A, it is conveyed while being gently curved, so that no excessive stress is applied to the sheet P. Also, when the sheet P is drawn into the pull-in passage B, switched back and guided to the discharge passage C, the sheet P is guided almost horizontally, so that no excessive stress is applied. Further, since the sheet P conveyed through the discharge path C is also gently curved and conveyed and discharged onto the sheet stacking tray 14, the sheet P is not excessively stressed. Since the sheet P does not pass through the U-turn path having a small radius of curvature in this way, even if the apparatus is downsized, the sheet P is not excessively stressed, and various sheets including a highly rigid sheet are used. be able to.

  Since the toner image formed on the sheet P is fixed twice by the fixing device 6, the fixing temperature of the fixing device 6 can be lowered and the power consumption can be reduced. Since the fixing temperature of the fixing device 6 can be lowered, it is possible to suppress heat from being accumulated in the desk 100 without providing a separate heat exhausting unit.

  FIG. 7 is an explanatory diagram for explaining the configuration and operation of the sheet detection sensor S2. FIG. 8 is a timing chart regarding the position of the sheet detection sensor S <b> 2, the switching member 80, and the conveyance direction of the fixing device 6.

  First, the configuration of the sheet detection sensor S2 will be described with reference to FIG. As shown in FIG. 7A, the sheet detection sensor S <b> 2 includes a sensor lever 91 that is rotatably supported by an inlet guide 27 disposed in the vicinity of the inlet of the fixing device 6, and a photo interrupter 92. Further, the sheet detection sensor S2 includes a tension spring 93 for returning the sensor lever 91 to the initial position after passing the sheet P.

  The sensor lever 91 includes a contact portion 91a that comes into contact with the sheet P, a light shielding portion 91b that shields the photo interrupter 92, and a spring hook portion 91c on which the tension spring 93 is hooked.

  Next, operation | movement of sheet | seat detection sensor S2 is demonstrated, referring FIG. 7 along the time chart of FIG.

  In a state in which the sheet P is not conveyed, the light shielding portion 91b of the sensor lever 91 shields the photo interrupter 92 (CLOSE), thereby detecting the absence of the sheet. At this time, the switching member 80 has moved to the first position while being rotated in the direction of arrow D1 in FIG. The pressure roller 26 of the fixing device 6 rotates in the direction of arrow R2 in FIG.

  Next, when the sheet P is conveyed in the forward direction (D3 direction in FIG. 7B) and the contact portion 91a of the sensor lever 91 is pushed by the leading end and the sheet surface of the sheet P and rotated in the direction of the arrow R5, The light from the photo interrupter 92 is transmitted (OPEN). Thereby, the presence of a sheet is detected. At this time, since the tension spring 93 is stretched and receives a moment in the direction of the arrow R7 due to the restoring force of the tension spring 93, it returns to the initial position after passing through the sheet P. And since the light-shielding part 91b of the sensor lever 91 light-shields (CLOSE) the photo interrupter 92, the absence of a sheet | seat is detected. As a result, the control device 39 rotates the switching member 80 in the direction of the arrow D2 in FIG. 6 and moves it to the second position.

  Next, before the sheet P is detached from the fixing device 6, the pressure roller 26 of the fixing device 6 rotates in the reverse direction in the direction of arrow R3 in FIG. 6, and the sheet P rotates in the reverse direction in the direction of arrow D4 in FIG. It is conveyed to. As a result, the sensor lever 91 rotates in the direction of the arrow R6, the light of the photo interrupter 92 is transmitted (OPEN), and the presence of a sheet is detected.

  At this time, since the tension spring 93 is stretched and receives a moment in the direction of the arrow R8 due to the restoring force of the tension spring 93, it returns to the initial position again after passing through the sheet P. Then, since the light shielding portion 91b of the sensor lever 91 shields (CLOSE) the photo interrupter 92, the switching member 80 rotates in the direction of arrow D1 in FIG. 6 to move to the first position, and waits for the next sheet.

  When the image formation for a predetermined number of sheets is completed and the sheet detection sensor S3 (FIG. 1) detects the trailing edge of the final sheet, the drive to each actuator is stopped and the printer main body 50A enters a standby state.

  Next, a case where the cartridge G is replaced will be described. FIG. 9 is an explanatory diagram showing a state where the cartridge G is being taken out by the printer 50.

  The cabinet 201 of the desk 100 in which the printer main body 50A is accommodated is provided with a fixed rail 105, and a roller 104 for sliding along the fixed rail 105 is rotatably fixed to the printer main body 50A. Yes. As a result, the printer main body 50A can slide in the direction of the arrow D11. Simultaneously with the pulling-out operation of the printer main body 50A, the guide member 21 rotates about the shaft 21a in the direction of the arrow R11 to open the discharge passage C. As a result, jamming of the discharge passage C becomes possible. Thereby, maintainability improves.

  The sheet stacking tray 14 is supported by the printer main body 50A so that it can be opened and closed. The cassette 15 is housed in the printer main body 50A and is supported so as to be pulled out in a substantially horizontal direction.

  Then, the cassette 15 storing the sheet P is slid out in the direction of the arrow D11 and pulled out, and the sheet stacking tray 14 is opened, so that the cartridge G is exposed. As a result, the user can easily replace (remove) the cartridge G. Then, by removing the cartridge G from the printer main body 50A, the main transport path A can be opened, and the main transport path A can be jammed. Thereby, maintainability improves.

  The desk 100 and the printer main body 50A are provided with power supply connectors 110 and 111 that face each other, and the power supply to the printer 50 is cut off when the printer main body 50A is pulled out.

  Although the present invention has been described based on the above embodiment, the present invention is not limited to this.

  In the above-described embodiment, the case where the sheet is switched back before the sheet is detached from the fixing device 6 is described, but the present invention is not limited to this. A pair of conveyance rollers that can be conveyed in the forward and reverse directions is arranged separately in the drawing path B so that the sheet can be conveyed to the fixing device 6 again even if the sheet is detached from the fixing device 6.

1 is an explanatory diagram showing a schematic configuration of a laser beam printer as an example of an image forming apparatus according to an embodiment. It is explanatory drawing which shows the state which accommodated the laser beam printer in the desk. FIG. 6 is an explanatory diagram illustrating a state where a sheet is being fed from a sheet feeding device. FIG. 4 is an explanatory view showing the vicinity of the photosensitive drum in FIG. 3. FIG. 6 is an explanatory view showing the vicinity of a fixing device that performs the first fixing. FIG. 6 is an explanatory diagram illustrating the vicinity of a fixing device that performs second fixing. It is explanatory drawing for demonstrating a structure and operation | movement of a sheet | seat detection sensor. 6 is a timing chart regarding a sheet detection sensor, a position of a switching member, and a conveyance direction of a fixing device. FIG. 6 is an explanatory diagram illustrating a state where a process cartridge is being removed from the printer.

Explanation of symbols

3 Exposure section (exposure equipment)
6 Fixing part (fixing device)
14 Sheet stacking unit (sheet stacking tray)
15 Sheet storage (cassette)
50 Image forming device (printer)
50A Device main body (printer main body)
100 Machine A Main transport passage B Retraction passage C Discharge passage G Image forming part (process cartridge)
R space S2 detector (sheet detection sensor)

Claims (7)

In an image forming apparatus that includes an image forming unit that forms a toner image on a sheet, fixes the toner image formed on the sheet by the image forming unit, and discharges the sheet from the apparatus main body.
A sheet stacking unit that is disposed at an upper part of the apparatus main body and stacks sheets discharged from the apparatus main body;
A sheet storage unit that is disposed between the sheet stacking unit and the image forming unit and stores sheets;
A fixing unit disposed below the image forming unit and fixing a toner image formed on the sheet by the image forming unit;
A drawing path that is disposed on the side of the fixing unit and draws in order to switch back a sheet on which the toner image is fixed by the fixing unit;
The sheet stored in the sheet storage unit is conveyed downward, a toner image is formed on the sheet by the image forming unit, and the toner image is once fixed on the sheet on which the toner image is formed by the fixing unit. The toner image is fixed by the fixing unit again after being pulled into the drawing path, and the sheet having the toner image fixed thereon is conveyed upward and discharged to the sheet stacking unit.
An image forming apparatus. A main conveyance path that is formed to extend downward from the sheet storage unit and guides the sheet from the sheet storage unit to the fixing unit via the image forming unit;
A discharge passage that is formed so as to extend upward from the fixing unit substantially parallel to the main conveyance path, and that guides the sheet that has passed through the fixing unit from the pull-in passage to the sheet stacking unit,
The image forming apparatus according to claim 1. Forming the main transport passage and the discharge passage curved in the same direction, and forming the pull-in passage substantially horizontally;
The image forming unit is disposed on the inner side of the main transport path, and the discharge path is disposed on the outer side of the main transport path.
The sheet on which the toner image is formed in the image forming unit through the main conveyance path is once switched with the image forming surface facing upward, the toner image is fixed by the fixing unit, and pulled into the drawing path, and then switched back. Then, the toner image is fixed by the fixing unit again, and the sheet on which the toner image is fixed is discharged to the sheet stacking unit through the discharge passage with the image forming surface facing downward.
The image forming apparatus according to claim 2. The image forming unit has an image carrier that carries a toner image on the surface,
An exposure unit that exposes the surface of the image carrier to form an electrostatic latent image on the surface of the image carrier;
The sheet storage portion and the pull-in passage are arranged to face each other,
The exposure unit is disposed in a space sandwiched between the sheet storage unit and the drawing passage,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The image forming unit is a process cartridge that is detachable from the apparatus main body,
The sheet stacking portion is supported by the apparatus main body so as to be freely opened and closed,
The sheet storage portion is supported by the apparatus main body so as to be freely drawn out in a substantially horizontal direction,
When the process cartridge is attached or detached, the sheet stacking unit is opened and the sheet storage unit is pulled out to expose the process cartridge in an accessible manner.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The fixing unit is capable of conveying a sheet in a forward direction in which the sheet is fed into the pull-in path and in a reverse direction in which the sheet is fed out from the pull-in path.
In the vicinity of the entrance where the sheet that has passed through the image forming unit in the fixing unit is introduced, a detection unit that detects the presence or absence of the sheet is provided,
When the sheet is conveyed by the fixing unit in the forward direction, and the absence of the sheet is detected by the detection unit, the sheet is conveyed in the reverse direction by the fixing unit before the sheet is removed from the fixing unit. ,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The apparatus main body is configured to be storable on a desk so that the sheet stacking unit is exposed on the desk.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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