JP4693654B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In recent years, manufacturers of image forming devices such as laser printers using electrophotography have lined up a large number of models with different customer groups and price ranges according to required performance and functions such as processing speed and duplex printing. ing. Large-scale models for business use that are particularly costly are equipped with an in-machine cooling fan or a cooling fan for automatic paper cooling on both sides after fixing, and they are discharged outside the machine due to the flow of wind. Since the steam is blown out vigorously, it does not stand out as white smoke.

  However, in small consumer-use models that have been reduced in cost and space, the number of cooling fans and the density of members around the fixing are conspicuous, and the flow of wind has become weak.

  In Patent Document 1, since the paper discharge path has only one system for face-down paper discharge, when the louver is closed with a shielding plate, water vapor is discharged from the face-down paper discharge outlet in search of the escape port. Can not be prevented.

Also, in the type with two paper discharge paths, face-down paper discharge and face-up paper discharge, the face-up paper discharge port is near the fixing device, so there is no wind flow around the face-up paper discharge port. Then white smoke becomes a problem.
JP 2002-366102 A (paragraph 0022, FIG. 6)

  Accordingly, an object of the present invention is to make white smoke inconspicuous by generating an air flow by using a branch guide switching operation of a paper discharge path.

  In order to achieve the above object, the present invention provides an image forming apparatus having a branch guide for switching the discharge direction of a recording medium after fixing a toner image to two or more directions. In a continuous image forming operation, the recording medium is conveyed through a discharge path. After passing through the branch guide, the switching operation of the branch guide is performed at least once before the next recording medium reaches the discharge path.

  Also, in the image forming operation within 10 minutes from the power-on of the image forming apparatus, the temperature inside the machine is low and the water vapor generated during fixing tends to become white smoke. Alternatively, it may be performed based on detection information of the fixing temperature sensor.

  The branch guide includes a plurality of guide ribs arranged in parallel at a predetermined interval, and the transport direction length of the plane portion connecting between the adjacent guide ribs is ½ or more of the transport direction length of the guide space plane. By setting so as to be, it is possible to increase the air volume of the air flow by the switching operation of the branch guide.

  According to the present invention, in a continuous image forming operation, after the recording medium is transported through the discharge path and passes through the branch guide, the branch guide is provided at least once before the next recording medium reaches the face-down discharge path. The switching operation is performed, thereby causing an air flow to disperse the water vapor discharged from the discharge port of the recording medium, thereby making white smoke inconspicuous.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an image forming apparatus (in this embodiment, an electrophotographic laser beam printer) including a process unit according to an embodiment of the present invention.

  The image forming apparatus (laser beam printer) 1 transfers a toner image formed on a photosensitive drum 2 as an image carrier by an electrophotographic image forming process onto a recording medium (paper, OHP sheet, etc.) 3 to form an image. Form.

  More specifically, the rotating photosensitive drum 2 is charged by a charger 4 having a charging roller 4a as a charging means, and then a laser beam corresponding to image information input from the exposure device 5 to the photosensitive drum 2. To form an electrostatic latent image on the photosensitive drum 2 according to the image information. The exposure device 5 reflects laser light emitted from a laser diode (not shown) according to image information by a polygon mirror (not shown) that rotates at high speed, and passes through a lens (not shown) and a reflection mirror (not shown). The surface of the photosensitive drum 2 is scanned and exposed.

  The electrostatic latent image is developed with toner (developer) of the developing device 6 having the developing roller 6a to form a toner image. The toner used as a developer used in this embodiment is a one-component magnetic toner in which magnetic particles are dispersed in a resin.

  In synchronism with the formation of the toner image, the recording medium 3 such as paper of a predetermined size set in a plurality of feeding cassettes 7 is made up of a pickup roller 8, a feed roller, and a retard roller that presses the recording medium 3. The feed path r1 is fed by the roller pair 9, and the pre-registration conveyance path r2 is conveyed by the reversing roller set 10 including the reversing roller and the two driven rollers in contact with the reversing roller. The recording medium 3 conveyed on the pre-registration conveyance path r2 is detected by the pre-registration detection switch 28, and based on this, the main body control unit (not shown) controls the operation of the registration roller pair 11, and the registration roller pair 11 performs toner. The pre-transfer conveyance path r3 is conveyed so as to match the image transfer timing, and reaches the transfer nip portion between the photosensitive drum 2 and the transfer roller 12 as a transfer means.

  Then, the toner image formed on the photosensitive drum 2 is transferred to the first surface of the recording medium 3 by the transfer roller 12 to which a transfer bias is applied. Thereafter, the recording medium 3 to which the toner image has been transferred is transported by a transport guide 13 through a pre-fixing transport path r4 and transported to a fixing device 14 as a fixing unit. The fixing device 14 includes a pressure roller 14c and a heating roller 14b incorporating a heater 14a, and fixes the recording medium 3 onto which the toner image has been transferred at a fixing nip portion between the pressure roller 14c and the heating roller 14b. The transferred toner image is fixed by applying heat and pressure to the recording medium 3 passing while being nipped and conveyed to the rear conveying path r5.

  Then, the swingable branch guide 20 is moved to the position indicated by the solid line in FIG. 1, and the upper roller of the transport roller set 15 composed of the upper, middle, and lower rollers that press the recording medium 3 on which the toner image is fixed. The face-down discharge path r6 is conveyed by the roller 15a, the intermediate roller 15b, and the conveying roller pair 16, and the face on which the image is recorded by the discharge roller pair 17 is placed on the lower side (so-called face-down). Discharge. The face-down discharge tray 18 is provided on the upper surface of the image forming apparatus main body 19. The swingable branch guide 20 is moved to the dotted line position in FIG. 1 to transport the face-up discharge path r 7, and the recording medium 3 on which the toner image is fixed by the discharge roller pair 21 is placed on the side surface of the image forming apparatus main body 19. The face-up discharge tray 22 can also be discharged with the surface on which the image is recorded facing upward (so-called face-up).

  FIG. 2 is a front view (a) and a side view (b) of the branch guide 20. As shown in FIG. 2, the branch guide 20 includes a plurality of boomerang-shaped guide ribs 20a arranged in parallel at a predetermined interval. Adjacent guide ribs 20a are connected by a plane portion 20b divided into three. Oscillating shafts 20c are provided on the outer surfaces of the guide ribs 20a located at both ends of the line. A force point pin 20d connected to a solenoid (not shown) is provided in the vicinity of one of the swing shafts 20c. Therefore, when the solenoid is turned ON / OFF, the force point pin 20d moves a predetermined distance about the swing shaft 20c, and the branch guide 20 swings between the solid line position and the dotted line position in FIG.

  As will be described later, the branch guide 20 can reciprocate repeatedly in a short time to generate an air flow with a fan in the flat portion 20b. At this time, it is possible to increase the air volume of the air flow by setting the length d of the plane portion 20b in the conveyance direction as long as possible, for example, to be not less than ½ of the conveyance direction length L of the guide space plane. it can.

  When recording images on both sides of the recording medium 3, when the recording medium discharged from the fixing device 14 is sandwiched between the conveyance roller pair 16 and the rear end of the recording medium 3 passes the branch guide 20, The conveyance roller pair 16 is reversed to convey the switchback path r8, and the recording medium 3 is conveyed on the duplex conveyance path r9 by the middle roller 15b and the lower roller 15c of the conveyance roller set 15 and the conveyance roller pairs 23, 24, and 25. Then, after reaching the reversing roller set 10, a toner image is formed on the second surface of the recording medium 3 in the same manner as described above, and then discharged to the face-down discharge tray 18 or the face-up discharge tray 22.

  After the toner image is transferred to the recording medium 3, the residual toner on the photosensitive drum 2 is removed by the cleaning roller 26a of the cleaning device 26 to prepare for the next image forming operation. The removed residual toner is moved to a waste toner collecting section in the cleaning device 26 by a waste toner collecting roller 26b that is driven to rotate and collected. Reference numeral 27 in FIG. 1 denotes a toner cartridge that stores unused toner and supplies the toner to the developing device 6 as necessary.

  Next, with respect to a mechanism for suppressing white smoke caused by water vapor generated from the recording medium and discharged outside the apparatus at the time of fixing the toner image, a case where face-up discharge or face-down discharge is performed after single-sided printing will be described with reference to FIGS. This will be described with reference to FIG. FIG. 3 is a control block diagram related to white smoke suppression control of the image forming apparatus according to the present embodiment. FIG. 4 is a schematic cross-sectional view of the image forming apparatus around the fixing unit for explaining the white smoke suppression operation during face-down discharge, and FIG. 5 is a diagram for explaining the white smoke suppression operation during face-up discharge. 2 is a schematic cross-sectional view of an image forming apparatus around a fixing unit. FIG.

  As shown in FIG. 3, in addition to the pre-registration detection switch 28, the main body control unit 30 passes the fixing device 14 (see FIG. 1) and then passes through the post-fixing conveyance path r5 (see FIG. 1). FIG. 1 shows a post-fixing detection switch 29 (see FIG. 1), an in-machine temperature sensor 32 for detecting the temperature in the apparatus main body, an in-machine humidity sensor 33 for detecting the humidity in the apparatus main body, and the temperature around the fixing device 14. Based on the signal output from the fixing temperature sensor 34 for detecting the ON / OFF operation of the solenoid 31 for swinging the branch guide 20 is controlled. With this configuration, when the solenoid 31 is ON, the main body control unit 30 holds the branch guide 20 in the upright posture as shown by the solid line position in FIG. 1, closes the face-up discharge path r7, and the post-fixing conveyance path. When r5 and the face-down discharge path r6 are opened and the solenoid 31 is OFF, the branch guide 20 is held in a recumbent posture as shown by the dotted line position in FIG. 1, and the face-down discharge path r6 is closed and conveyed after fixing. It operates to open the path r5 and the face-up discharge path r7.

  When the face-down discharge is performed, the first recording medium 3 on which the toner image is fixed is detected by the pre-registration detection switch 28 (the pre-registration detection switch 28 is turned on), as shown in FIG. As described above, the main body control unit 30 turns on the solenoid 31, holds the branch guide 20 in the standing posture, and guides the first recording medium 3 to the face-down discharge path r6. Then, 500 msec after the pre-registration detection switch 28 is turned off, as shown in FIG. 4B, the solenoid 31 is turned off with the rear end of the recording medium 3 being in contact with the branch guide 20, and the branch guide 20 is in the lying position. Rocks.

  If the pre-registration detection switch 28 is in the ON state by the second recording medium 3, as shown in FIG. 4C, the solenoid 31 is turned ON, and the branch guide 20 is again swung to the standing posture. Conversely, if the pre-registration detection switch 28 is in an OFF state, the solenoid 31 is turned on and then immediately turned off to check the state of the pre-registration detection switch 28. Thereafter, if the pre-registration detection switch 28 is in the OFF state, the operation is repeated.

  Accordingly, in a continuous image forming operation, after the recording medium 3 is transported through the face-down discharge path r6 and passes through the branch guide 20, it is at least 1 until the next recording medium 3 reaches the face-down discharge path r6. The turn-branch guide 20 is swung quickly in a reciprocating manner, thereby causing an air flow to disperse water vapor discharged from the face-up discharge port, thereby making white smoke inconspicuous.

  On the other hand, when face-up discharge is performed, the first recording medium 3 on which the toner image is fixed is detected by the pre-registration detection switch 28 (the pre-registration detection switch 28 is turned on). As shown, the main body control unit 30 turns off the solenoid 31, holds the branch guide 20 in the lying position, and guides the first recording medium 3 to the face-up discharge path r7. Then, 500 msec after the post-fixing detection switch 29 is turned off, as shown in FIG. 5B, the solenoid 31 is turned on at the timing when the rear end of the recording medium 3 is separated from the discharge roller pair 21, and the branch guide 20 is turned on. Swing to a standing posture.

  When the pre-registration detection switch 28 is in the ON state by the second recording medium 3, as shown in FIG. 5C, the solenoid 31 is turned off and the branch guide 20 is again swung into the lying posture. Conversely, if the pre-registration detection switch 28 is in an OFF state, the solenoid 31 is turned off and then immediately turned on to check the state of the pre-registration detection switch 28. Thereafter, if the pre-registration detection switch 28 is in the OFF state, the operation is repeated.

  Accordingly, in a continuous image forming operation, after the recording medium 3 is transported through the face-up discharge path r7 and passes through the branch guide 20, it is at least 1 until the next recording medium 3 reaches the face-up discharge path r7. The turn-branch guide 20 is swung quickly in a reciprocating manner, thereby causing an air flow to disperse water vapor discharged from the face-up discharge port, thereby making white smoke inconspicuous.

  Further, in the image forming operation within 10 minutes after the power of the image forming apparatus 1 is turned on, the in-machine temperature is low and the water vapor generated at the time of fixing tends to become white smoke. Therefore, the in-machine temperature sensor 32, the in-machine humidity sensor 33, the fixing temperature sensor. 34, respectively, and it is determined by OR condition whether the in-machine temperature is 20 ° or less, the in-machine humidity is 70% or more, or the fixing temperature sensor is 10 ° or less. In this case, the solenoid 31 is repeatedly turned on and off, and the branch guide 20 is swung back and forth to generate an air flow.

  The present invention can be used in an image forming apparatus.

FIG. 1 is a schematic configuration diagram showing an image forming apparatus (in this embodiment, an electrophotographic laser beam printer) including a process unit according to an embodiment of the present invention. These are the front view (a) and side view (b) of a branch guide. These are control block diagrams related to the white smoke suppression control of the image forming apparatus according to the present embodiment. FIG. 3 is a schematic cross-sectional view of an image forming apparatus around a fixing unit for explaining white smoke suppression operation during face-down discharge. FIG. 3 is a schematic cross-sectional view of an image forming apparatus around a fixing unit for explaining white smoke suppression operation during face-up discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Recording medium 4 Charging device 4a Charging roller 5 Exposure apparatus 6 Developing apparatus 6a Developing roller 7 Feed cassette 8 Pickup roller 9 Feeding roller pair 10 Reversing roller set 11 Registration roller pair 12 Transfer roller 13 Conveying guide 14 Fixing device 14a Heater 14b Heating roller 14c Pressure roller 15 Conveying roller set 15a Upper roller 15b Middle roller 15c Lower roller 16 Conveying roller pair 17 Discharging roller pair 18 Face-down discharging tray 19 Image forming apparatus main body 20 Branch guide 20a Guide rib 20b Flat surface portion 20c Oscillating shaft 20d Force point pin 21 Discharge roller pair 22 Face-up discharge tray 23, 24, 25 Conveying roller pair 26 Cleaning device 26a Cleaning roller 26b Waste toner collecting roller 2 8 Pre-registration detection switch 29 Post-fixing detection switch 30 Main body control unit 31 Solenoid 32 In-machine temperature sensor 33 In-machine humidity sensor 34 Fixing temperature sensor r1 Feeding path r2 Pre-registration conveying path r3 Pre-transfer conveying path r4 Pre-fixing conveying path r5 After fixing Conveyance path r6 Face-down discharge path r7 Face-up discharge path r8 Switchback path r9 Double-sided conveyance path

Claims (3)

  In an image forming apparatus having a branch guide for switching the discharge direction of a recording medium after toner image fixing to two or more directions, after the recording medium is transported through the discharge path and passed through the branch guide in a continuous image forming operation, the next recording medium The image forming apparatus is characterized in that the switching operation of the branch guide is performed at least once before the toner reaches the discharge path.   The image forming apparatus according to claim 1, wherein the branch guide switching operation is performed based on detection information of an in-machine temperature sensor, an in-machine humidity sensor, or a fixing temperature sensor.   The branch guide includes a plurality of guide ribs arranged in parallel at a predetermined interval, and the length in the transport direction of the plane portion connecting the adjacent guide ribs is ½ or more of the transport direction length of the guide space plane. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to be

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