JP4701955B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a printer, a copying machine, a multi-function machine, etc. that forms an image by forming a toner image by using an electrophotographic method and the like, and finally transferring it as an unfixed toner image to a sheet-like material and then fixing it. In particular, the present invention relates to an improvement of an image forming apparatus provided with a mechanism for avoiding the peripheral surface of a heating rotating body in a fixing apparatus that performs fixing from abrasion or damage due to contact of a peeling claw. is there.

  In the image forming apparatus as described above, as the fixing device, a heating roll and a pressure roll that are press-contacted so as to form a fixing nip portion that allows a sheet-like object such as paper carrying an unfixed toner image to pass therethrough. And a peeling claw that is urged so that the tip of the claw contacts the peripheral surface of the heating roll and swings and peels the sheet after passing through the fixing nip from the heating roll. Many fixing devices are used.

  In an image forming apparatus using such a fixing device, since the peeling claw in the fixing device is always in contact with the peripheral surface of the rotating heating roll, the peripheral surface portion to which the peeling claw contacts is worn. As a result, there is a problem that streaks or black lines with changed glossiness (gloss) are included in the fixed image corresponding to the worn portion, or a linear local fixing defect occurs. Also, when a paper jam occurs in the fixing device, the jammed paper often presses the peeling claw strongly against the heating roll. In this case, the circumferential surface of the heating roll is damaged by the peeling claw. Therefore, it may be necessary to replace the heating roll unscheduled.

  In order to solve such a problem, the following proposals have been made in the prior art.

For example, the tip of the separation claw is displaced in the direction away from the fixing roller by the tension of the paper that is nipped and conveyed between the paper discharge roller and the fixing roller that is set to a peripheral speed faster than the peripheral speed of the paper discharge roller. A fixing device provided with a protruding portion protruding in the paper conveyance path is proposed (Patent Document 1). According to this fixing device, it is possible to secure the separation state of the separation claw with respect to the fixing roller without using any special parts or devices, and to easily prevent the adverse effects caused by the continuous contact of the separation claw.

  Further, in order to solve the problem in the fixing device proposed in Patent Document 1, a part of the peeling claw installed so as to be able to swing is projected between the paper discharge guides, When the paper transported between the auxiliary rollers is transported between the paper discharge guides, the front end of the paper hits the protruding portion of the peeling claw and passes with the protruding portion displaced by the rigidity of the paper. Accordingly, there has been proposed a fixing device in which the peeling claw is swung in the direction of separating from the heating roller by the displacement of the protruding portion (Patent Document 2). According to this fixing device, the peeling claw can be quickly separated from the heating roller without requiring the tension of the paper as in the fixing device proposed in Patent Document 1, thereby causing the heating roller to be worn or damaged. It is said that can be prevented.

  Further, the rear end portion of the peeling claw installed so as to be able to swing is extended, and the extended end portion is rotated around the rotation shaft on the driven roller side that is displaced by the passage of the paper among the discharge roller pair that discharges the paper after fixing. When the sheet after fixing enters and is conveyed to the discharge roller pair, the rotation shaft on the driven roller side is displaced so that the peeling claw is moved through the extended end portion to the tip end portion of the claw Has been proposed (Patent Document 3) which is configured to swing in a direction away from the heating roller. According to this fixing device, it is possible to prevent the toner from adhering to the peeling claw and the occurrence of damage to the fixing roller and the peeling claw.

JP 58-7167 A JP-A-64-981 Japanese Patent No. 2672514

  However, the fixing device proposed in Patent Documents 1 to 3 has the following problems.

  That is, in the fixing device proposed in Patent Document 1, since a sheet in which tension is generated during nipping and conveyance is brought into contact with the protruding portion formed on the peeling claw, the fixed image on the sheet is in contact with the protruding portion. There is a problem such as rubbing due to contact, resulting in streaks in the fixed image.

  Further, in the fixing device proposed in Patent Document 2, since the paper immediately after fixing is brought into contact with the protruding portion of the peeling claw and conveyed, the image immediately after fixing on the paper is in contact with the protruding portion. There is a problem such as a streak in the fixed image. In addition, since the protruding portion of the peeling claw exists in the path of the sheet immediately after fixing, the traveling direction of the sheet is temporarily disturbed, or the leading end of the sheet is bent due to contact with the protruding portion. There is a risk that. Moreover, since the leading edge of the sheet immediately after fixing is decelerated due to contact with the protruding portion of the peeling claw, the rear side of the sheet becomes curved or wavy, so in the worst case There is also a risk that unexpected jams may be triggered by this condition.

  Furthermore, since the fixing device proposed in Patent Document 3 is provided with a part of the peeling claw extended to the discharge roller pair, the peeling claw itself becomes large, and the fixing device is downsized. Is disadvantageous. In addition, the mechanism in which the driven roller of the discharge roller pair is displaced by the entry and passage of the paper is such that the driven roller is positioned on the rotation shaft of the driving roller so that the lower end portion of the driven roller and the upper end portion of the driving roller have a stepped state. Since the driven roller is lifted and displaced so that the stepped state disappears when the paper enters, the driven roller is lifted when the paper enters the discharge roller pair. As a result, the leading edge of the paper is decelerated by lifting the driven roller as the paper enters the discharge roller pair, and in this relationship, the rear side of the paper is curved or waved. In the worst case, there is a risk of causing an unexpected jam.

  The present invention has been made in view of the above-described problems. An unnecessary line or the like is added to a fixed image after fixing by a fixing device, or a sheet-like material such as paper after fixing is added. Provided is an image forming apparatus capable of avoiding a conveyance failure or clogging as much as possible from wear or damage caused by contact of a peeling claw on a peripheral surface of a heating rotor during fixing. .

An image forming apparatus according to the present invention (first invention) forms an image based on image information and finally transfers it as an unfixed toner image to a sheet-like material, and the image forming apparatus transfers the image. A heating rotator and a pressure rotator that are press-contacted to form a fixing nip portion through which a sheet-like material carrying an unfixed toner image passes, and a claw tip is in contact with the peripheral surface of the heating rotator. And a fixing device provided with a peeling claw for peeling the sheet-like material after passing through the fixing nip portion from the heating rotating body, and being discharged from the fixing device. A pair of transport rolls that transport the sheet-like material sandwiched for the first time, and the fixing nip portion installed in a transport path between the pair of transport rolls and the heating rotating body and the pressing rotating body of the fixing device. Remove the sheet after passing An image forming apparatus having a guide member for guiding toward the conveying roller pair,
The conveyance speed of the pair of conveyance rolls is set to be faster than the conveyance speed of the heating rotator and the pressure rotator, and the toner image is fixed on the surface of the guide member after the fixing of the sheet-like material. A part existing on the opposite side is configured as a swing guide member that can swing due to the tension of the sheet-like material when transported in a state straddling the pair of transport rollers and the fixing nip, and A rotating body that rotates in contact with the sheet-like material is rotatably provided at a portion of the rocking guide member that is in contact with the sheet-like material conveyed in the straddled state. In other words, an interlocking separation mechanism is provided that swings the peeling claw in a direction in which the claw tip portion is separated from the peripheral surface of the heating rotating body.

  Here, the setting relating to the conveyance speed may be set so as to always have such a speed relationship, but only when the content is specific fixing (for example, when the sheet-like material is of a type other than cardboard). The swing guide member that may be set needs to be configured to be swingable by the tension of the sheet-like material. The rotating body is preferably in the form of a roll, but may be other than this. The interlocking separation mechanism may be any mechanism that can separate the peeling claw using the swinging motion of the swing guide member. The sheet-like material may be any material that can carry out a normal fixing process by carrying a toner image and passing through the fixing nip portion.

  Further, the image forming apparatus of the present invention (second invention) is a claw for the peeling claw in conjunction with the swinging motion of the swing guide member, instead of the interlocking separation mechanism in the image forming apparatus of the first invention. An interlocking reduction mechanism is provided that displaces a biasing member for biasing the tip portion so as to come into contact with the peripheral surface of the heating rotating body in a direction in which the biasing force is reduced.

  Here, a coil spring or the like is usually used as the biasing member, but other members may be used. The interlock reduction mechanism may be any mechanism that can displace the biasing member of the peeling claw in a direction in which the biasing force is reduced by using the swinging motion of the swing guide member.

  In the image forming apparatuses according to the first and second aspects of the present invention, the rotating body of the swing guide member in the fixing device is always more than the guide surface of the other guide member existing in the vicinity of the swing guide member. It is good to set so that it may protrude in the conveyance path | route side of a sheet-like article. The other guide member is, for example, a guide rib.

  In such a configuration, even when the swinging guide member swings due to the tension of the sheet-like material conveyed in the straddled state, the sheet-like material comes into contact with the rotating body and contacts other guide members. Since there is no contact, there is no possibility that the fixed image surface of the sheet-like material may have streaks or the like due to contact with other guide members and induce poor image quality.

  Furthermore, in the image forming apparatus according to each of the first and second inventions described above, the swing guide member in the fixing device has an axis of the swing shaft at the same position as an axis of the swing shaft of the peeling claw. It is good to install so that it becomes.

  In such a configuration, the swing guide member in the interlocking separation mechanism and the interlocking reduction mechanism is unitized with the peeling claw so that the structure can be simplified and the assembling work can be simplified. In addition, the swinging motion of the swing guide member can be easily transmitted to the peeling claw and its biasing member because of the relationship of swinging around the same axis, and the positional accuracy of the swing guide member can be improved by suppressing the accumulated variation in dimensions. It becomes easy to improve.

  According to such an image forming apparatus of the first and second inventions, when the sheet-like material after fixing by the fixing device is conveyed in a state straddling between the conveying roll pair and the fixing nip portion, The swing guide member swings due to the tension of the object, and the swinging movement makes use of the swinging movement of the peeling claw tip to be separated from the heating rotating body by the interlocking separation mechanism, or the peeling claw tip by the interlocking reduction mechanism. The urging force (pressure, load) when the part comes into contact with the heating rotator is reduced.

  Moreover, when the swing guide member is swung by the tension of the sheet-like material when transported in the straddled state, the sheet-like material is in contact with the rotating body instead of the swing guide member. .

  As a result, in this image forming apparatus, although the peeling claw is temporarily separated or the urging force is reduced in spite of the fixing operation, the heating rotator is brought into contact with the tip of the peeling claw. As a result, the wear on the peripheral surface is reduced, and as a result, the occurrence of streak-like image quality failure or fixing failure on the fixed image due to local wear of the heating rotator is prevented. Further, since the sheet-like object is in contact with the rotating body on the swing guide member, this also prevents the occurrence of streak-like image quality defects on the fixed image.

[Embodiment 1]
FIG. 1 shows a main part of an image forming apparatus according to Embodiment 1 of the present invention.

  The image forming apparatus 1 constitutes a laser printer using, for example, an electrophotographic system. The printer 1 includes an image forming unit 10 that forms a toner image T and transfers the toner image T to a sheet P inside the main body 2, and a sheet P that carries an unfixed toner image T transferred by the image forming unit 10. A fixing device 20A that passes the toner image T and fixes the toner image T, and a paper conveying device 30 that supplies the paper P to the image forming unit 10 or conveys it to a predetermined part, etc. are appropriately distributed and installed. Has been.

  The image forming unit 10 includes a photosensitive drum 11 as an image carrier, a charging roll 12 as a charging unit, a laser scanning device (ROS) 13 as an image exposing unit, a developing unit 14 as a developing unit, and a charging unit. And a cleaning device 16 as a cleaning means.

  The photosensitive drum 11 is formed by forming a photosensitive layer made of an organic photosensitive material or the like on the peripheral surface of a conductive drum that is rotatably supported. When an image forming operation (printing) is performed, a driving device (not shown) drives the photosensitive drum 11 in the direction of the arrow. It is driven to rotate at a predetermined speed. The circumferential surface of the photosensitive drum 11 is uniformly charged by the charging roll 12, and then the laser beam (LB) modulated based on image information is scanned from the laser scanning device 13 on the charged surface. An electrostatic latent image is formed by exposure. The laser scanning device 13 operates based on an image signal obtained after a predetermined process is performed in the image processing device 17 installed in the main body 2 on image information appropriately input from the outside.

  Subsequently, the electrostatic latent image on the photosensitive drum 11 is developed (unfixed) with a developer (toner) supplied from the developing device 14 to be a toner image, and then the toner image is at a predetermined timing. It is transferred onto the supplied paper P by the transfer roll 15. The peripheral surface of the photosensitive drum 11 after the transfer is cleaned by removing unnecessary materials such as residual toner and paper dust attached to the peripheral surface by the cleaning device 16.

  The paper P is accommodated in the paper feed cassette 31 (stacked on the bottom plate 31a), and is sent out from the paper feed cassette 31 one by one by the feed roll 32a and the retard roll 32b, and then the registration roll pair. Up to 33. Thereafter, the paper P is supplied toward the transfer position (between the photosensitive drum 11 and the transfer roll 15) by the resist roll pair 33 in anticipation of the transfer timing of the toner image. The paper P on which the unfixed toner image T has been transferred at the transfer position is then conveyed toward the fixing device 20A and fixed.

  The paper P on which the toner image T has been fixed by passing through the fixing device 20A is discharged from the fixing device 20 and then is directly discharged onto the discharge tray 35 by the discharge roll pair 34. This completes basic printing.

  When performing duplex printing, when the paper P after fixing is not discharged onto the discharge tray 35 and the rear end of the paper is sandwiched between the discharge roll pair 34, the discharge roll pair 34 is reversed. At the same time, by switching the transport destination switching gate 36, the paper P is sent from the rear end side to the double-sided transport path 37, and retransmitted to the registration roll 34 with the front and back surfaces reversed through the double-sided transport path 37. Is done. Thereafter, printing on the second surface is performed by passing through the image forming unit 10 and the fixing device 20 as described above.

  Next, the fixing device 20A in the printer 1 will be described.

  The fixing device 20A includes a heating roll 22 installed to rotate in the main body 21 and a fixing nip portion N that allows the sheet P carrying the unfixed toner image T to pass through the heating roll 22 in pressure contact therewith. And a peeling claw 26 for peeling the paper P after passing through the fixing nip portion N from the heating roll 22 are mainly installed.

  The heating roll 22 has a core metal 22a formed into a relatively thin cylindrical shape with a metal such as aluminum or stainless steel, and a release property such as tetrafluoroethylene or PFA coated on the outer peripheral surface of the core metal 22a. It is composed of a release layer 22b made of a material, and a halogen heater 24 as a heating source is installed inside the roll (the hollow portion of the cored bar 22a). The heating roll 22 is maintained at a predetermined temperature (fixing temperature, standby temperature, etc.) by controlling the energization state to the halogen heater 24 based on detection information from the temperature sensor 25 that measures the roll surface temperature. Heated to sag. Further, the heating roll 22 is rotationally driven at a predetermined speed in the direction of the arrow in response to the rotational power of a rotational driving device (not shown).

  The pressure roll 23 includes a metal core 23a formed in a solid or hollow cylindrical shape with a metal such as stainless steel or aluminum, and a heat-resistant elastic layer 23b made of silicone rubber or the like formed on the outer peripheral surface of the metal core 23a. And a release layer 23b made of a release material such as tetrafluoroethylene or PFA, which is coated on the surface of the elastic layer 23b. The pressure roll 23 is supported so as to be brought into pressure contact with the heating roll 22 that is rotationally driven by a pressure mechanism (not shown) at a predetermined pressure.

  In this fixing device 20A, the heating roll 22 and the pressure roll 23 are installed in a horizontal state (horizontal placement), and are pressed in this state to form a fixing nip N. For this reason, the sheet P at the time of fixing is conveyed so as to rise from the lower side of the fixing device 1 toward the fixing nip portion N as shown by an alternate long and short dash line in FIG. After that, the sheet is transported so as to rise upward, and is transported along a substantially vertical transport path as a whole. In FIG. 2 and the like, reference numeral 27 denotes a paper introduction guide plate on the entrance side of the fixing nip N.

  As shown in FIGS. 2 to 4, the peeling claw 26 is disposed at a position slightly retracted downstream of the outlet of the nip portion N in the rotation direction of the heating roll 22, and the claw tip 26 a It is swingably attached to the support shaft 41 so as to be in contact with the peripheral surface of the heating roll 22, and toward the heating roll 22 (dotted arrow direction B) by a torsion coil spring 42 attached to the support shaft 41. And elastically biased at a predetermined pressure. Further, the peeling claw 26 has a guide surface portion 26b formed in a shape substantially parallel to the sheet conveyance path (dashed line) continuously from the claw tip portion 26a. A plurality of the peeling claws 26 are used, and are installed in a state where they are distributed to predetermined positions appropriately selected in the axial direction of the heating roll 22. In FIG. 3, an alternate long and short dash line denoted by reference numeral 41 a is the axis of the support shaft 41.

  Further, on the exit side of the fixing device main body 21, a plurality of first discharge side guide plates that guide the fixed sheet P toward the discharge roll pair 35 side on the same side as the separation claw 26 as viewed from the conveyance path of the sheet P. 28 are installed at positions appropriately distributed along the axial direction of the heating roll 22. The first discharge side guide plate 28 is installed in a state facing both sides of the peeling claw 26. Further, the discharge-side guide plate 28 returns again to the heating roll 22 side from the upward inclined guide surface portion 28a inclined so as to approach the pressure roll 23 side from the peeling claw 26 and the end point (uppermost position) of the upward inclined guide surface 28a. As a whole, the lower inclined guide surface portion 28b that is inclined has a guide surface that has a gentle mountain shape.

  Further, on the outlet side of the fixing device main body 21, a second guide member 29 is provided on the pressure roll 23 side so as to face the first discharge side guide plate 28 (in the upward inclined guide surface portion 28a). The second guide member 29 has an inclined guide surface portion 29a that is inclined from the pressure roll 23 side to the first discharge side guide plate 28 side and gradually approaches the upward guide surface portion 28a of the guide plate. Yes.

  In addition, between the outlet side of the fixing device 20A and the discharge roll pair 35, the fixed sheet P is guided to the discharge roll pair 35 on the same side as the first discharge side guide plate 28 with respect to the paper conveyance path. A discharge path fixing guide plate 38 is installed. The discharge path fixing guide plate 38 is guided in a gentle curve from the vicinity of the end point (lowermost position) of the downward inclined guide surface portion 28b of the first discharge side guide plate 28 to the discharge roll pair 35 disposed obliquely above. It has a guide surface portion 38a.

  Further, between the outlet side of the fixing device 20A and the discharge roller pair 34, the transfer destination switching gate 36 and the discharge path movable guide plate described above are on the same side as the second discharge side guide plate 29 with respect to the sheet transfer path. 39 is installed along the paper transport path.

  The transport destination switching gate 36 is formed from the vicinity of the end point position of the guide surface portion 29a of the second discharge side guide plate 29 and the first half area of the downward inclined guide surface portion 28b of the first discharge side guide plate 28 and the guide surface portion 38a of the discharge path fixing guide plate 38. A discharge path guide surface portion 36a extending opposite to the discharge path guide surface portion 36a, and a double-sided conveyance path guide surface 36b on the opposite side of the discharge path guide surface portion 36a, with a support shaft 36c at the end on the fixing device 20A side as a center. To swing. Further, the discharge path movable guide plate 39 extends from the vicinity of the end point position of the guide surface portion 36a of the transport destination switching gate 36 to the discharge roller pair 34 so as to face the latter half region of the guide surface portion 38a of the discharge path fixing guide plate 38. It has a guide surface portion 39a and swings around a support shaft 39b at the end on the discharge roll pair 34 side.

  The transport destination switching gate 36 and the discharge path movable guide plate 39 are normally positioned so as to face the first discharge guide plate 28 and the discharge path fixed guide plate 39 to form a paper discharge path. When transporting to the transport path 37, the transport destination switching gate 36 swings downward while the discharge path movable guide plate 39 swings upward and the guide surface portions 36b and 39a face each other. It moves to a position where a paper transport path communicating with the transport path 37 is formed.

  In the fixing device 20A, as shown in FIGS. 2 to 4, the peeling claw 26 is moved to the tip end portion of the claw in conjunction with the swinging motion of the guide guide plate that can swing freely among the plurality of guide guide plates. An interlocking separation mechanism 50 that swings in a direction in which 26 a separates from the circumferential surface of the heating roll 22 is provided.

  In this interlocking separation mechanism 50, first, the first discharge guide plate 28 is attached to the same support shaft 41 as the peeling claw 26 (on the end portion side where the upward inclined guide surface portion 28a is provided) and retracted from the paper conveyance path (dotted line). It is configured as a swing guide plate (51) that can be swung and displaced in the direction of arrow C), and is the most protruding portion of the first discharge guide plate 28 toward the sheet transport path, that is, its upward inclined guide surface portion 28a. A guide roller 52 as a guide member is rotatably attached to the connecting portion of the downward inclined guide surface portion 28b.

  Normally, the first discharge guide plate 28 is placed at the guide position in a state where it is elastically biased toward the paper transport path side by a biasing means such as a coil spring. In addition, when the first discharge guide plate 28 swings to the side retracted from the paper conveyance path, another member (for example, a paper conveyance rib or the like) installed on the outlet side of the fixing device main body 21 in the axial direction of the heating roll 22. The maximum swinging position is regulated so that it is maintained (stopped) in the same protruding height state as in any of the above) or in a state in which it protrudes to the inside of the transport path. The guide rollers 52 are in the form of a roll, and are formed at the connecting portions of the up-tilt guide surface portion 28a and the down-tilt guide surface portion 28b of the two first discharge guide plates 28 that are opposed to each other with the peeling claw 26 interposed therebetween. It is rotatably attached to the bearing groove 28c. At this time, the guide roller 52 is attached in a state in which the peripheral surface protrudes to the sheet conveyance path side from any of the guide surface portions of the first discharge guide plate 28.

  Further, in the interlocking separation mechanism 50, when the first discharge guide plate 28 swings to the side of retreating from the paper conveyance path, it protrudes to the opposite side to the claw tip 26a side with the support shaft 41 of the peeling claw 26 interposed therebetween. A pressing portion 53 is formed to press the swinging claw 26 so as to contact the swinging protrusion 43 formed so as to swing.

  The first discharge guide plate 28 as the swing guide plate 51 swings due to the tension generated on the paper P when the fixed paper P is conveyed in a state straddling the discharge roll pair 34 and the fixing nip N. It is like that. In this printer 1, in order to generate tension on the paper P in this transport state, the transport speed (V1) of the discharge roll pair 34 is set higher than the transport speed (V2) of the heating roll 22 and the pressure roll 22. Fast speed is set (V1> V2).

  Next, the operation of the fixing device 20A provided with such an interlocking separation mechanism 50 will be described.

  At the time of fixing, the sheet P on which the unfixed toner is transferred on the image forming unit 10 side enters the fixing nip portion N between the heating roll 22 and the pressure roll 23 heated to the fixing temperature and rotating in the direction of the arrow. It is introduced while being guided by the side paper introduction guide plate 27 (FIG. 2). The unfixed toner image T is fixed by being fused to the paper P by being heated and pressurized when passing through the fixing nip N.

  The paper P discharged from the fixing nip N after the completion of the fixing is peeled off from the heating roll 22 by itself or by the peeling action of the peeling claw 26, as shown in FIGS. Passing through a discharge passage formed between the plate 28 and the discharge path fixed guide plate 38, the second discharge guide plate 29, the transfer destination switching gate 36, and the discharge path movable guide plate 39 toward the discharge roll pair 34 side. Are transported.

  At this time, the leading end portion Pa of the paper P normally reaches the guide roller 52 while being guided by the first discharge guide plate 28 at the guide position, and thereafter, in contact with the guide roller 52 and the discharge destination switching gate 36 and the discharge. The traveling guide plate 39 guides the traveling direction so as to be bent obliquely upward, and proceeds toward the discharge roll pair 34 side. At this time, since the guide roller 52 is in the form of a roll, the guide roller 52 comes into contact with the sheet P on the surface and easily rotates so as to follow the contact with the moving sheet P. Thereby, even if the fixed image surface side of the paper P contacts the guide roller 52, a problem such as a streak in the image does not occur.

  When the leading end Pa side of the sheet P reaches the discharge roll pair 34 and is conveyed while being sandwiched between the rolls, the conveyance speed (V1) of the discharge roll pair 34 is heated as shown in FIG. Since the conveyance speed (V2) of the roll 22 and the pressure roll 22 is faster, the sheet P is in a state where it is straddled between the discharge roll pair 34 and the fixing nip portion N and is strongly pulled by the discharge roll pair 34. become.

  Tension is generated in the portion Pb of the paper P conveyed in a state straddling between the discharge roll pair 34 and the fixing nip portion N. As a result, the sheet portion Pb straddling the sheet portion Pb is stretched to take the shortest path in the discharge passage between the discharge roll pair 34 and the fixing nip portion N. The first discharge guide plate 28 protruding in the inside is pushed through the guide roller 52, and the entire first discharge guide plate 28 is retracted from the discharge passage around the support shaft 41 (arrow direction C). Swing.

  As a result, the interlocking separation mechanism 50 pushes the pressing portion 53 of the swinging first discharge guide plate 28 so as to abut the swinging protrusion 43 of the peeling claw 26 and swing the peeling claw 26. . As a result, the entire peeling claw 26 also oscillates in the direction of arrow C about the support shaft 41 in conjunction with the oscillating movement of the first discharge guide plate 28, so that the claw tip 26 a is separated from the heating roll 22. It will be in a state (FIG. 4, FIG. 6).

  Accordingly, in the fixing device 20A, the peeling claw 26 is separated from the heating roll 22 by the interlocking separation mechanism 50 in spite of the fixing operation. Therefore, the heating roll 22 by the contact of the peeling claw tip 26a. The wear on the peripheral surface is reduced. This also reduces the wear on the peeling claw tip 26a. For this reason, it is possible to prevent the occurrence of streak-like image quality failure or fixing failure in the fixed image due to local wear of the heating roll 22.

  Further, in the fixing device 20A, even when the first discharge guide plate 28 is swung by the tension of the paper portion Pb when transported in the straddling state, the paper portion Pb is not moved to the first discharge guide plate 28. Since the contact roller 52 is in contact with the guide roller 52 at the most protruding position in the paper conveyance path instead of the guide surface portion, unnecessary streaks or the like may not enter the fixed image. Further, since the guide roller 52 is formed so as to protrude from other components such as guide ribs existing in the vicinity thereof, the paper portion Pb does not contact any part other than the guide roller 52. This also eliminates the possibility of unnecessary streaks entering the fixed image.

  Further, in this fixing device 20A, until the leading end portion Pa of the paper P after fixing reaches the discharge roll pair 34, it only passes through the normal discharge path, and the path is blocked by particularly strongly contacting the guide member or the like. Therefore, there is no fear that the conveyance speed will decrease, and there is no possibility that an unexpected jam will be induced as the conveyance speed is reduced. Even if an unexpected jam occurs, the jammed paper is buckled in a bellows shape and pushes the guide plate 28 and the rotating body 52 to separate the peeling claw 26 from the heating roll 22. The peeling claw 26 is strongly pressed against the heating roll 22 by being pressed, and there is no possibility that the peripheral surface of the heating roll 22 is damaged.

  Finally, in the fixing device 20A provided with the interlocking separation mechanism 50, the tension of the paper portion Pb disappears when the rear end portion of the paper P is completely discharged from the fixing nip portion N. Then, the first discharge guide plate 26 that has been swung by the tension of the sheet is swung in the direction of arrow B and returned to the guide position. Further, in conjunction with the swinging motion of the first discharge guide plate 26 at the time of return, the peeling claw 26 also swings in the direction of arrow B so that the claw tip 26a is in contact with the peripheral surface of the heating roll 22. Will return.

[Embodiment 2]
FIG. 7 shows a part of the printer (fixing device and discharge unit) according to the second embodiment of the present invention.

  The fixing device 20B in this printer has the same configuration as the fixing device 20A in the printer 1 of the first embodiment, except that the interlocking reduction mechanism 60 is provided in place of the interlocking separation mechanism 50 and changed. For this reason, in FIG. 7 and the like, the same reference numerals are given to the portions common to the printer 1 and the fixing device 20A according to the first embodiment, and the description of the common components is omitted below. is doing.

  The interlocking reduction mechanism 60 in the fixing device 20B displaces the urging member of the peeling claw 26 in a direction in which the urging force is reduced in conjunction with the swinging motion of the guide guide plate that is freely swingable among the plurality of guide guide plates. It is something to be made.

  The interlock reduction mechanism 60 in this example employs the first discharge guide plate 28 as in the case of the interlocking separation mechanism 50 as a swingable guide guide plate (61) as shown in FIGS. Further, as a biasing member (62) for biasing the claw tip 26a of the peeling claw 26 so as to come into contact with the peripheral surface of the heating roll 22, a support shaft can be used instead of the torsion coil spring 42 in the first embodiment. 41 between the swinging arm part 45 extending to the opposite side of the claw tip 26a side of the peeling claw 26 and the swinging tip part of the first discharge guide plate 28 (the end part of the downwardly inclined guide surface part 28b). The tension coil spring 46 that hooks the end portions (46a, 46b) was used.

The tension coil spring 46 is attached at a position where the tensile force of the coil spring 46 is directed to the peeling claw 26 via the swinging arm portion 45 in the direction of the arrow B with the support shaft 41 as the center (the claw tip 26a is the heating roll 22). As long as the first discharge guide plate 28 swings about the support shaft 41 as shown in FIG. Any position that can satisfy the condition (L1> L2) that the distance L2 between the attachment positions of both ends (L2) is shorter than the total length L1 before the swing (when in the guide position) is sufficient.

  However, the attachment position that satisfies this condition is that the tension of the coil of the tension coil spring 46 causes the peeling claw 26 to be centered on the support shaft 41 via the oscillating arm portion 45 and the arrow B direction (the claw tip 26a is a heating roll). 22 only in the case where the conditions for acting in such a manner as to swing in the direction of contact with the head 22 are satisfied at the same time. Further, when the tension coil spring 46 is at the guide position before swinging and is in the state of the full length L1, the claw tip 26a of the peeling claw 26 can be brought into contact with the peripheral surface of the heating roll 22 with a normal pressure. I can do it.

  Next, the operation of the fixing device 20B provided with such an interlock reduction mechanism 60 will be described.

  First, the fixing operation of the unfixed toner image T onto the paper P by the fixing device 20B is performed in the same manner as the fixing device 20B in the first embodiment (FIG. 2) (FIG. 7). Further, the operation when the fixed sheet P is conveyed toward the discharge roll pair 34 is performed in the same manner as in the case of the fixing device 20B in the first embodiment (FIG. 5) (FIG. 8).

  Then, when the leading end Pa side of the sheet P after fixing reaches the discharge roll pair 34 and is transported while being sandwiched between the rolls, the transport speed of the discharge roll pair 34 is as shown in FIGS. Since (V1) is faster than the conveying speed (V2) of the heating roll 22 and the pressure roll 22, the paper P is in a state of straddling between the discharge roll pair 34 and the fixing nip portion N, and by the discharge roll pair 34. It will be pulled strongly. Due to the tension generated in the portion Pb of the paper P conveyed in a state straddling between the discharge roller pair 34 and the fixing nip portion N, as in the case of the first embodiment, the paper is protruded in the discharge passage. A certain first discharge guide plate 28 is pushed through the guide roller 52, and the entire first discharge guide plate 28 swings around the support shaft 41 toward the side retracted from the discharge passage (arrow direction C).

As a result, the interlocking reduction mechanism 60 causes the attachment end 46b of the tension coil spring 46 on the swinging tip side of the swinging first discharge guide plate 28 to swing (the position indicated by reference numeral 46c in FIG. 8). ). That is, the tension length of the tension coil spring 46 changes from L1 to L2 in association with the swinging movement of the first discharge guide plate 28 (L1> L2). As a result, the tensile force of the tension coil spring 46 at the full length L2 is weaker than that at the full length L1, so that the urging force for swinging the peeling claw 26 about the support shaft 41 in the arrow B direction is also weak. Finally, the pressure (load) when the claw tip 26a contacts the peripheral surface of the heating roll 22 is reduced (FIGS. 8 and 10).

  Accordingly, in the fixing device 20B, the pressure when the claw tip portion 26a of the peeling claw 26 contacts the heating roll 22 is reduced by the interlocking reduction mechanism 60 even though the fixing operation is being performed. The wear on the circumferential surface of the heating roll 22 due to the contact of the peeling claw tip 26a is reduced. This also reduces the wear on the peeling claw tip 26a. For this reason, it is possible to prevent the occurrence of streak-like image quality failure or fixing failure in the fixed image due to local wear of the heating roll 22. Other than this, the same effects as those of the fixing device 20A in the first embodiment can be obtained.

FIG. 11 shows the results of measurement of the amount of wear at the portion where the peeling claw tip 26a of the heating roll 22 contacts (slidably contacts) with respect to the number of sheets of paper P that have been fixed (running number). This measurement result is obtained when the biasing force of the coil spring 46 that biases the tip end portion 26a of the peeling claw in the direction in contact with the heating roll is normal (when the coil spring 46 is in a normal position) and when it is reduced. (Measured when the coil spring 46 is in the swing position). As is apparent from this result, by reducing the urging force when the tip end portion 26a of the peeling claw is brought into contact with the heating roll, wear of the peripheral surface portion where the peeling claw tip portion 26a of the heating roll 22 contacts is reduced. I understand that From this, it can be analogized that the wear of the distal end portion 26a of the peeling claw 26 is also reduced at the same time by reducing the urging force.

Finally, also in the fixing device 20B provided with the interlocking reduction mechanism 60, when the rear end portion of the paper P is completely discharged from the fixing nip portion N, the tension of the paper portion Pb disappears. Therefore, the first discharge guide plate 26 that has been oscillated by the tension of the paper oscillates in the direction of arrow B and returns to the guide position, and is linked to the oscillating motion when the first discharge guide plate 26 is returned. Hari overall length of the coil spring 4 6 tensile and also returns to L1. As a result, the peeling claw 26 tensile obtain a regular urging force of the coil spring 4 6 swings in the direction of the arrow B the pawl tip 26a is returned to the contacting state in the normal pressure on the circumferential surface of the heating roll 22 It will be.

[Other embodiments]
In the first and second embodiments, the case where the first discharge guide plate 28 as the swinging guide member is coaxially attached to the support shaft 41 of the peeling claw 26 is illustrated as an example. 28 may be configured to be attached to a support shaft provided at a position different from the support shaft 41 of the peeling claw 26.

FIG. 2 is a schematic explanatory diagram illustrating a main part of an image forming apparatus (printer) according to Embodiment 1 (2). FIG. 2 is a partial cross-sectional explanatory diagram illustrating a fixing device and a discharge unit in the first embodiment. It is a perspective view which shows the structure of an interlocking separation mechanism. It is explanatory drawing which shows the structure and operation state of an interlocking separation mechanism. FIG. 6 is an explanatory diagram illustrating a state of an interlocking separation mechanism and the like before a sheet after fixing reaches a pair of discharge rolls. FIG. 6 is an explanatory diagram illustrating a state of an interlocking separation mechanism or the like when a sheet after fixing is conveyed in a state straddling between a discharge roll pair and a fixing nip portion. FIG. 6 is a partial cross-sectional explanatory diagram illustrating a fixing device and a discharge unit according to a second embodiment. It is a perspective view which shows the structure of an interlocking reduction mechanism. FIG. 6 is an explanatory diagram illustrating a state of an interlocking reduction mechanism and the like before a sheet after fixing reaches a discharge roll pair. FIG. 6 is an explanatory diagram illustrating a state of an interlock reduction mechanism or the like when a sheet after fixing is conveyed in a state of straddling between a discharge roll pair and a fixing nip portion. It is a graph which shows the measurement result regarding the wear amount of the site | part which the peeling nail | claw tip part of a heating roll contacts with respect to a paper travel amount when the strength of urging force is changed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 10 ... Image forming unit (image forming apparatus), 20A, 20B ... Fixing device, 22 ... Heating roll (rotating body for heating), 23 ... Pressing roll (rotating body for pressing), 26 ... peeling claw, 26a ... claw tip, 28, 51, 61 ... first discharge guide plate (swing guide member), 34 ... discharge roll (conveying roll pair), 38 ... discharge path fixing guide plate (guide member) , 41 ... support shaft (oscillating shaft), 41a ... shaft center, 4 6 ... tension coil spring (biasing member), 50 ... interlocking separation mechanism, 52 ... guide roller (rotating body), 60 ... interlocking reduction mechanism, T ... unfixed toner image, P ... paper (sheet-like material), N ... fixing nip, C ... one swinging direction (separating direction or reducing direction).

Claims (3)

An image forming device that forms a toner image based on image information and finally transfers the toner image as an unfixed toner image to a sheet-like material;
A heating rotator and a pressure rotator that are pressed against each other so as to form a fixing nip portion through which a sheet-like material carrying an unfixed toner image transferred by the image forming apparatus passes, and a periphery of the heating rotator. Fixing provided with a peeling claw that is urged so that the tip of the claw comes into contact with the surface and swings and peels off the sheet-like material after passing through the fixing nip from the heating rotator. Equipment,
A pair of conveying rolls that convey the sheet-like material discharged from the fixing device for the first time;
The sheet-like material that has been installed in the conveyance path between the conveyance roller pair and the heating rotator and the pressure rotator of the fixing device and has passed through the fixing nip portion is guided to the conveyance roll pair. An image forming apparatus having a guide member
The transport speed of the transport roll pair is set to a speed faster than the transport speed of the heating rotator and the pressurizing rotator,
In addition, when a part of the guide member that is present on the side facing the carrying surface side of the toner image after fixing of the sheet-like material is transported across the pair of transport rollers and the fixing nip portion, It is configured as a swing guide member that can swing due to the tension of the sheet-like material, and is in contact with a portion of the swing guide member that comes into contact with the sheet-like material conveyed in the straddled state. A rotating rotating body is rotatably provided,
And the biasing force of the biasing member for the pawl tip of the separation claw in conjunction the swing motion is biased into contact with the peripheral surface of the heating rotating body of the swing guide member alleviation the interlocking relief mechanism for displacing in the direction provided,
The interlock reduction mechanism uses a tension coil spring as the urging member, and is formed so that one end of the tension coil spring extends to the opposite side of the claw tip side with the swinging shaft of the peeling claw interposed therebetween. When the swing guide member swings and the other end is attached to the swinging tip side of the swing guide member and the tension length of the tension coil spring after swinging is An image forming apparatus, wherein the image forming apparatus is attached so as to satisfy a condition of being shorter than a tension length before moving . The rotating body of the swing guide member is set so as to always protrude toward the conveyance path of the sheet-like material from the guide surfaces of other guide members existing in the vicinity of the swing guide member. Item 2. The image forming apparatus according to Item 1 . 3. The image forming apparatus according to claim 1 , wherein the swing guide member is installed such that an axis of the swing shaft is located at the same position as an axis of the swing shaft of the peeling claw .

Images