JP2015087696A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can suppress the deposition of toner on a sheet peeling member to prevent image defects due to a residual toner, and an image forming apparatus including the same.SOLUTION: A fixing unit 6 has a peeling pawl 63 that peels a sheet P from a pressure roller 62, a contact/separation mechanism 64 that performs the contact/separation operation of the peeling pawl 63, and a control unit 65 that controls the contact/separation mechanism 64. The control unit 65 brings the peeling pawl 63 into contact with the pressure roller 62 when the leading end of the sheet P passes through the peeling pawl 63, and separates the peeling pawl 63 from the pressure roller 62 before the rear end of the sheet P passes through the peeling pawl 63.

Description

  The present invention relates to a fixing device provided in an electrophotographic image forming apparatus, and more particularly to a fixing device having a peeling claw for paper peeling and an image forming apparatus provided with the fixing device.

  A conventional fixing device includes a sheet peeling member that contacts the surface of the fixing roller in order to peel the conveyed sheet from the fixing roller. In such a fixing device, in order to suppress the wear of the sheet peeling member and the damage to the fixing roller, there has been proposed one in which the sheet peeling member can be brought into contact with and separated from the surface of the fixing roller. In such a fixing device, the sheet peeling member is separated from the fixing roller every time a sheet is conveyed.

  By the way, in a fixing device provided with such a paper peeling member, toner accumulated between the paper peeling member and the fixing roller (hereinafter referred to as residual toner) is reattached to the fixing roller at the start of rotation of the fixing roller, and is conveyed. There was a problem of soiling the incoming paper. Japanese Patent Application Laid-Open No. 2004-133867 describes not only suppressing the wear of the sheet peeling member and damage to the fixing roller, but also suppressing the occurrence of image defects due to residual toner using a sheet peeling member separation / contact mechanism. Yes.

  That is, the fixing device of Patent Document 1 is configured to count the number of sheets conveyed to the fixing device and to separate the sheet peeling member from the fixing roller every time a predetermined number of fixings are performed. As a result, the fixing device of Patent Document 1 separates the sheet peeling member from the fixing roller before a large amount of residual toner is deposited on the sheet peeling member, and separates the residual toner accumulated by the separating operation from the sheet peeling member.

JP 2011-28097 A

  The fixing device disclosed in Patent Document 1 is configured to separate the residual toner accumulated by the separating operation of separating the sheet peeling member from the fixing roller from the sheet peeling member. However, such a configuration is effective only when the toner is easily separated from the sheet peeling member. When the separation property of the toner from the paper peeling member is low, rather, the contact time between the paper peeling member and the fixing roller becomes longer, so that more toner is deposited on the paper peeling member and image defects are likely to occur. Problems arise.

  Even if the sheet peeling member is separated from the fixing roller every time a sheet is conveyed, the sheet conveying interval is reduced in recent image forming apparatuses in order to increase the process speed. There is little time for the sheet peeling member to be separated from the fixing roller during operation. For this reason, a sufficient effect for preventing toner accumulation on the sheet peeling member cannot be expected.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device capable of suppressing toner accumulation on a sheet peeling member and preventing image defects due to residual toner, and an image forming apparatus including the same. And

  The fixing device of the present invention is a fixing device including at least one of a pressure rotating member or a heating rotating member, and is provided so as to be able to contact and separate from the pressure rotating member or the heating rotating member. A sheet peeling member for peeling the sheet from the sheet, a separation / contact mechanism for performing the separation / contact operation of the sheet separation member, and a control unit for controlling the separation / contact mechanism, wherein the front end of the sheet is the sheet The sheet peeling member is brought into contact with the rotating member when passing through the peeling member, and the sheet peeling member is separated from the rotating member before the trailing edge of the sheet passes through the sheet peeling member.

  According to the above configuration, since the sheet peeling member is separated from the rotating member such as the heating roller or the pressure roller before the trailing edge of the sheet passes, the sheet peeling member is brought into contact with the rotating member while the sheet is passing. Compared to the case, the contact time between the sheet peeling member and the rotating member can be further reduced. Thus, the contact time between the paper peeling member and the rotating member provided with the member can be minimized as much as possible without impairing the paper peeling performance, and the residual toner can be prevented from being deposited on the paper peeling member.

  In the fixing device, the control unit may control the operation timing of the separation / contact mechanism using a drive signal of a sheet conveying member provided on the upstream side of the fixing device as a trigger.

  According to the above configuration, in order to detect the leading edge position of the paper P, a sensor for performing the detection is omitted by using a paper transport member (for example, a PS roller) provided on the upstream side of the fixing device. can do.

  Further, in the fixing device, the control unit removes the sheet peeling member from the rotating member simultaneously with the start of driving of the pressure rotating member and the heating rotating member when the operation is resumed after the jam processing or when the purge processing is performed after the jam occurs. The sheet peeling member can be separated from the rotating member after a predetermined time has elapsed from the start of driving of the pressure rotating member and the heating rotating member.

  According to the above configuration, even when a jammed paper is left after the jam processing, the remaining paper can be prevented from being wound around the rotating member when the operation is resumed. Alternatively, it is possible to prevent the sheet discharged during the purge process from being wound around the rotating member.

  Further, in the fixing device, the separation / contact mechanism is slidable parallel to the rotation shaft of the pressure rotation member or the heating rotation member, and a guide shaft having a notch formed on the outer peripheral surface thereof. And when the notch is located at a position facing the paper peeling member by sliding movement of the guide shaft, the paper peeling member is in contact with or separated from the rotating member, and the guide When the notch is in a position not facing the paper peeling member due to the sliding movement of the shaft, the paper peeling member can be in the other state of contacting or separating from the rotating member.

  According to the above configuration, since the peeling claw is separated and connected using the sliding guide shaft, the arrangement space can be reduced even if a drive source (for example, a solenoid) for sliding the guide shaft is included. Can do.

  In the fixing device and the image forming apparatus of the present invention, the sheet peeling member is separated from the rotating member such as the heating roller or the pressure roller before the trailing edge of the sheet passes, so that the sheet peeling member and the rotation provided with the member are rotated. The contact time with the member is reduced as much as possible, and it is possible to suppress the accumulation of residual toner on the sheet peeling member.

FIG. 3 is a diagram illustrating a general basic arrangement around a photosensitive drum in an image forming apparatus. FIG. 2 is a diagram illustrating a configuration and a function of a fixing device in the first embodiment. 6 is a timing chart of fixing / separating timing control of the fixing device in the first embodiment. FIG. 10 is a perspective view showing an appearance of a separation / contact mechanism in the second embodiment. FIG. 11 is a plan view showing the operation of the separation / contact mechanism in the second embodiment. FIG. 11 is a plan view showing the operation of the separation / contact mechanism in the second embodiment. It is an expansion perspective view which shows the connection part of the peeling nail | claw in Embodiment 2, and a separation / contact mechanism. It is an expansion perspective view which shows the connection part of the peeling nail | claw in Embodiment 2, and a separation / contact mechanism. FIG. 6 is a longitudinal sectional view schematically showing an overall configuration of a digital multifunction peripheral according to a third embodiment.

[Embodiment 1]
In the first embodiment, a fixing device to which the present invention is applied will be described with reference to the drawings. The fixing device according to the first embodiment is provided in an electrophotographic image forming apparatus. First, a general basic arrangement around the photosensitive drum in the image forming apparatus will be described with reference to FIG.

  The photosensitive drum 1 is a roller-like member provided so as to be rotatable around an axis in an arrow direction, and has a photosensitive film on which an electrostatic latent image and a toner image are formed. The charger 2 is a main charger provided to face the outer peripheral surface of the photosensitive drum 1, and charges the outer peripheral surface of the photosensitive drum 1 to a predetermined polarity and potential.

  The exposure device 3 (see FIG. 9) irradiates the charged photosensitive drum 1 with the signal light L corresponding to the image data. As a result, an electrostatic latent image corresponding to the image data is formed on the outer peripheral surface of the photosensitive drum 1.

  The developing device 4 supplies the toner T to the outer peripheral surface of the photosensitive drum 1 and visualizes the electrostatic latent image as a toner image. The transfer device 5 applies a transfer bias from the back surface of the recording paper P passing between the photosensitive drum 1 and the transfer device 5, and transfers the toner image onto the recording paper P.

  The fixing device 6 is disposed downstream of the transfer device 5 along the conveyance path of the recording paper P. The fixing device 6 heats and pressurizes the recording paper P passing through the fixing nip portion, thereby melting and fixing the toner image transferred to the recording paper P.

  The cleaning unit 7 scrapes and removes toner T, paper dust, and the like remaining on the outer peripheral surface of the photosensitive drum 1 from the outer peripheral surface of the photosensitive drum 1 with a cleaning blade. The static eliminator 8 irradiates light on the outer peripheral surface of the photosensitive drum 1 after the cleaning process by the cleaning unit 7 to optically neutralize the remaining charges.

  The fixing device according to the present invention is used as the fixing device 6 shown in FIG. A specific configuration and operation of the fixing device 6 will be described with reference to FIGS. 2 and 3.

  FIG. 2 is a diagram illustrating the configuration and function of the fixing device 6 according to the first embodiment. The fixing device 6 includes a heating roller 61 including a heater 61 a therein and a pressure roller 62 that is driven to rotate by the heating roller 61, and has a fixing nip portion between the heating roller 61 and the pressure roller 62. Further, the fixing device 6 includes a peeling claw (paper peeling member) 63 on the downstream side in the paper conveyance direction with respect to the pressure roller 62.

  The peeling claw 63 is driven by the separation / contact mechanism 64 and is provided so as to be able to contact and separate from the pressure roller 62. That is, when the leading edge of the conveyed paper passes through the peeling claw 63, the peeling claw 63 contacts the pressure roller 62 and is separated after passing. Thereby, the contact time between the peeling claw 63 and the pressure roller 62 can be reduced as much as possible, and accumulation of residual toner on the peeling claw 63 can be suppressed. In the first embodiment, the configuration in which the peeling claw 63 is provided for the pressure roller 62 is illustrated, but the present invention is not limited to this. The peeling claw 63 may be provided for the heating roller 61, or may be provided for both the heating roller 61 and the pressure roller 62. However, the pressure roller 61 having an elastic layer on the surface can be separated from the roller surface without damaging the roller, and is preferably used.

  The fixing device 6 includes a heating roller 61 and a pressure roller 62, and a fixing nip portion is provided between these rollers. However, the present invention is not limited to this, and at least one member forming the fixing nip portion may use, for example, a belt provided with a roller inside instead of the above-described roller.

  The peeling claw 63 accumulates residual toner as the contact time with the pressure roller 62 becomes longer during the operation of the fixing device 6. Therefore, in the fixing device 6, the peeling claw 63 is brought into contact with the pressure roller 62 just before the leading end in the conveyance direction of the conveyed paper P contacts the peeling claw 63, and the leading end of the paper P passes through the peeling claw 63. After that, it controls so that it may space apart quickly. That is, in the fixing device 6, the separation claw 63 is not separated from the pressure roller 62 after the entire sheet P has passed through the separation claw 63, but before the rear end of the sheet P passes the separation claw 63. 63 is separated from the pressure roller 62. When the leading edge of the paper P is peeled off from the pressure roller 62, the subsequent paper P is guided to the transport path by a transport guide member (not shown). Even if they are not in contact with each other, the paper is not wound around the pressure roller 62.

  Such separation / contact timing control is performed by the control unit 65 and the timer 66. In order to perform the above control, it is necessary to detect the leading end position of the paper P on the upstream side of the fixing device 6. In the first embodiment, a PS (Paper Stop) roller 9 (see FIG. 1) is used to detect the leading end position of the paper P. The PS roller 9 is a roller for temporarily stopping the sheet P upstream of the transfer unit 5 and feeding the sheet P in time with the toner image on the photosensitive drum 1. For this reason, the conveyance start timing by the PS roller 9 can be used for detecting the leading edge of the paper P. FIG. 3 shows a timing chart of the separation / contact timing control.

  A driving signal for the PS roller 9 is input to the control unit 65, and the control unit 65 causes the timer 66 to perform time measurement using this driving signal as a trigger. Then, the peeling claw 63 is brought into contact with the pressure roller 62 at time t2 after the elapse of time T1 (s) from the rise of the driving signal of the PS roller 9 (paper conveyance start by the PS roller 9: time t1), and further from time t2. The separation claw 63 is separated from the pressure roller 62 at time t3 after the elapse of time T2 (s). Time t <b> 2 indicates the timing just before the leading edge of the sheet contacts the peeling claw 63. Time t3 indicates the timing after the leading edge of the paper P has passed through the peeling claw 63 and before the trailing edge of the paper P has passed through the peeling claw 63. The time T1 and the time T2 are set in advance based on the distance from the PS roller 9 to the peeling claw 63 and the conveyance speed of the paper P.

  In the first embodiment, by using the PS roller 9 for detecting the leading end position of the paper P, a sensor for performing the detection can be omitted. However, the present invention is not limited to this, and a sensor for detecting the leading end position of the paper P may be arranged on the upstream side of the fixing device 6 and the above control may be performed based on the detection signal of this sensor. Good.

  In addition, when the image forming apparatus has a plurality of image forming modes having different sheet conveyance speeds, the time T1 and the time T2 may be changed according to the image forming mode. For example, when the image forming apparatus has a monochrome printing mode (high-speed printing) and a color printing mode (low-speed printing), the time T1 and the time T2 in the color printing mode are compared with the time T1 and the time T2 in the monochrome printing mode. Can be set longer.

  Although the above description has explained the separation / contact control of the peeling claw 63 during normal operation (during job printing), it is preferable that the separation / contact control of the peeling claw 63 is appropriately performed even during a jam. An example of the separation / contact control of the peeling claw 63 at the time of jam will be described as follows.

  As an example, when a jam occurs during printing and the jam processing is completed and the operation is resumed, the peeling claw 63 is brought into contact with the pressure roller 62 simultaneously with the start of driving of the heating roller 61, and a predetermined time (for example, After 1.5 s), the peeling claw 63 is separated. This is because there is a possibility that the jammed paper is left after the jam processing is performed, and the paper remaining when the operation is resumed is prevented from being wound around the pressure roller 62.

  The same operation is also performed when a purge process (a process of driving the heating roller 61 and discharging the paper in the transport path after jam notification) is performed when a jam occurs. That is, the peeling claw 63 is brought into contact with the pressure roller 62 simultaneously with the start of driving of the heating roller 61 for the purge process, and the peeling claw 63 is separated after a predetermined time (for example, 1.5 s).

[Embodiment 2]
In the second embodiment, a more detailed structural example of the separation / connection mechanism 64 will be described. FIG. 4 is a perspective view showing an appearance of the separation / connection mechanism 64. 5 and 6 are plan views showing the operation of the separation / connection mechanism 64. FIG. 7 and 8 are enlarged perspective views showing a connecting portion between the peeling claw 63 and the separating / connecting mechanism 64. FIG.

  The separation / connection mechanism 64 includes a solenoid 641, a swing member 642, and a guide shaft 643. The solenoid 641 is ON / OFF driven by the control unit 65 and slides the guide shaft via the swing member 642. The guide shaft 642 is disposed in parallel with the rotation shafts of the heating roller 61 and the pressure roller 62, and is slidable in parallel with this axial direction. Furthermore, the guide shaft 643 has a notch 643a on the outer peripheral surface.

  That is, as shown in FIGS. 5 and 6, the solenoid 641 is rotationally displaced by the ON / OFF driving. Further, the swing member 642 and the guide shaft 643 are coupled so that the rotational displacement of the swing member 642 is converted into the slide displacement of the guide shaft 643.

  As shown in FIGS. 7 and 8, the peeling claw 63 includes a claw portion 631 and a support portion 632. Further, the peeling claw 63 has a rotation shaft in the support portion 632 and can rotate around this shaft. Further, the peeling claw 63 is urged by a torsion spring 65 in a direction in which the claw portion 631 is brought into contact with the pressure roller 62.

  5 and 7 show a state in which the peeling claw 63 is in contact as the pressure roller 62. FIG. At this time, the solenoid 641 is turned ON, and the guide shaft 643 is moved to a position where the notch 643a is opposed to the peeling claw 63. In this state, the peeling claw 63 comes into contact with the pressure roller 62 by the biasing force of the torsion spring 65.

  6 and 8 show a state where the peeling claw 63 is separated as the pressure roller 62. At this time, the solenoid 641 is turned off, and the guide shaft 643 is moved to a position where the notch 643 a does not face the peeling claw 63. In this state, the support portion 632 of the peeling claw 63 is pressed in contact with the outer peripheral surface of the guide shaft 643, rotates against the urging force of the torsion spring 65, and is separated from the pressure roller 62.

  As described above, in the configuration of the separation / contact mechanism 64 that separates / contacts the separation claw 63 using the sliding guide shaft 643, the arrangement space can be reduced even if the solenoid 641 and the swing member 642 are included.

  In the above description, the notched portion 643a is in a contact state when facing the peeling claw 63, and is separated when the notched portion 643a is not facing the peeling claw 63, but the present invention is limited to this. Not. That is, conversely, a configuration may be adopted in which the notched portion 643 a is in a separated state when facing the peeling claw 63 and is in a contact state when the notched portion 643 a is not facing the peeling claw 63.

  In the fixing device 6, a plurality of peeling claws 63 and a plurality of notches 643 a in the guide shaft 643 are provided, and these peeling claws 63 perform a contact / separation operation synchronously. Thereby, in the image forming apparatus, the sheet peeling operation can be satisfactorily performed for all sizes of the usable paper P.

[Embodiment 3]
In the third embodiment, a configuration example of an image forming apparatus to which the fixing device described in the first and second embodiments is applied will be described. In the third embodiment, as an image forming apparatus, a digital multi-function peripheral 100 capable of printing a document read by the scanner 20 or printing image data input from an external device via a network is exemplified.

  FIG. 9 is a longitudinal sectional view schematically showing the overall configuration of the digital multifunction peripheral 100. The digital multifunction peripheral 100 includes a photosensitive drum 1, a charger 2, an exposure unit 3, a developing unit 4, a transfer unit 5, a fixing unit 6, a cleaning unit 7, a static eliminator 8, a scanner 20, a paper feed tray 21, and a paper discharge tray. 22 is included.

  The scanner 20 is provided with a document setting tray, an automatic document feeder (RADF, Reversing Automatic Document Feeder), and the like. The scanner 20 includes a document reading device, and the document reading device includes a document placing table and a document scanning device.

  The paper feed tray 21 is a tray that stores recording paper P such as plain paper, coated paper, color copy paper, and OHP film. A plurality of paper feed trays 21 may be provided, and each paper feed tray 21 may store recording paper P having different sizes. The recording paper P on which an image is formed is discharged and stacked on the paper discharge tray 22.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Exposure device 4 Developing device 5 Transfer device 6 Fixing device (fixing device)
7 Cleaning unit 8 Static eliminator 9 PS roller 61 Heating roller 62 Pressure roller 63 Peeling claw (paper peeling member)
64 Separation / detachment mechanism 65 Control part 66 Timer 631 Claw part 632 Support part 641 Solenoid 642 Swing member 643 Guide shaft 643a Notch

Claims (4)

A fixing device comprising at least one of a pressure rotating member or a heating rotating member,
A paper peeling member provided so as to be able to contact and separate from the pressure rotary member or the heating rotary member, and for peeling the paper from the rotary member;
A separation mechanism for performing a separation operation of the sheet peeling member;
A control unit for controlling the separation mechanism,
The control unit causes the paper peeling member to contact the rotating member when the leading edge of the paper passes through the paper peeling member, and rotates the paper peeling member before the trailing edge of the paper passes through the paper peeling member. A fixing device which is separated from a member. An image forming apparatus comprising the fixing device according to claim 1,
The image forming apparatus according to claim 1, wherein the control unit controls an operation timing of the separation / contact mechanism using a drive signal of a sheet conveying member provided on the upstream side of the fixing device as a trigger. An image forming apparatus comprising the fixing device according to claim 1,
The control unit causes the sheet peeling member to contact the rotating member simultaneously with the start of driving of the pressure rotating member and the heating rotating member when the operation is resumed after the jam processing or when the purge processing is performed after the jam occurs. An image forming apparatus, wherein the sheet peeling member is separated from the rotating member after a predetermined time has elapsed from the start of driving of the rotating member and the heating rotating member. An image forming apparatus comprising the fixing device according to claim 1,
The separation / contact mechanism has a guide shaft that is slidable parallel to the rotation axis of the pressure rotation member or the heating rotation member, and that has a notch formed on the outer peripheral surface thereof.
When the notch is in a position facing the sheet peeling member by the sliding movement of the guide shaft, the sheet peeling member is in a state of either contacting or separating from the rotating member,
The image forming apparatus, wherein the sheet peeling member is in contact with or separated from the rotating member when the notch is not opposed to the sheet peeling member by sliding movement of the guide shaft. .

Images