JP2007187715A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a fixing device capable of achieving the heating of the large capacity of compressed air without providing a heater used only for heating compressed air and a power source therefor, surely preventing gloss unevenness after fixing, and avoiding upsizing and cost rising. <P>SOLUTION: The fixing device is equipped with a heating roller heated by a predetermined heating member, a pressure roller pressuring the heating roller, and an air jet means arranged on a paper ejection side of a nip part formed by the heating roller and the pressure roller, and jetting the compressed air from an air nozzle to the leading edge of recording paper passing through the nip part so that the recording paper may be peeled from the heating roller. In the fixing device, a part of a flow path where the compressed air is made to flow to the air nozzle is arranged at a position at which the heat of the heating member is transmitted by heat conduction or heat radiation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device that heats and pressurizes unfixed toner on a recording paper and specifically fixes the air, and jets compressed air to the leading end of the recording paper that has passed through the nip portion to release the recording paper from a roller. The present invention relates to a fixing device including means.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions, a latent image corresponding to an original is formed on a photosensitive member, and toner is applied to the latent image. Thus, the visualized toner image is transferred onto the recording paper, and then the toner image transferred onto the recording paper is fixed and discharged.

  As a fixing device for fixing a toner image in this manner, a recording sheet on which a toner image is transferred is sandwiched between a nip portion formed by a heating roller incorporating a halogen heater and the like and a pressure roller that presses the heating roller. There is a fixing device of a heat roller fixing system that heats and pressurizes while conveying, and such a fixing device is widely used because of its simple configuration.

  In addition, an endless fixing belt is stretched between a heating roller incorporating a halogen heater or the like and a fixing roller, and has a pressure roller that presses the fixing roller through the fixing belt. There is a belt-fixing type fixing device that heats and pressurizes while pinching and transporting the recording paper onto which the toner image is transferred at the formed nip part. Such a fixing device has a small heat capacity of the fixing belt, so it warms up. It has the advantage of reducing time and saving energy.

  Here, since the toner of the toner image on the recording paper is heated when it passes through the nip portion, the toner acts like an adhesive, and the recording paper that has passed through the nip portion is not separated, and the heating roller or the fixing belt. There is a risk that the material adheres to the surface of the wire and winds, causing jamming. In particular, when a small amount of paper (thin paper) and a small amount of coated paper for printing are used as the recording paper, the separation performance is further deteriorated.

  For this reason, a fixing device having a peeling claw as shown in FIG. 8 is known.

  In FIG. 8, the toner image on the recording paper P is heated while being nipped and conveyed at a nip portion N formed by a heating roller 271 heated by a halogen heater H and a pressure roller 272 that presses the heating roller 271.・ Pressure is fixed. Further, a separation claw 201 is provided on the paper discharge side of the recording paper P with respect to the nip portion N, and a tip portion thereof is in pressure contact with the outer surface of the heating roller 271. Therefore, even if the recording paper P is wound around the heating roller 271 and discharged, the peeling claw 201 comes into contact with the leading end portion of the recording paper P, and the recording paper P is peeled off from the heating roller 271, so that the above problem is solved. .

  However, since the sharp tip of the peeling claw 201 is in pressure contact with the surface of the heating roller 271, the release layer formed of a fluororesin or the like that covers the surface of the heating roller 271 is worn by a relatively short period of use. Or the tip of the peeling claw 201 is worn, and if left as it is, a fixing failure occurs.

In order to solve such a problem, compressed air is jetted to the heating roller on the recording paper discharge side with respect to the nip portion, and the leading end of the recording paper wound around the heating roller is peeled off by the wind pressure of the compressed air. A fixing device is known (for example, see Patent Document 1).
JP 2005-157179 A

  In the fixing device disclosed in Patent Document 1, an air nozzle that ejects compressed air to the recording paper discharge side with respect to the nip portion to peel off the leading end portion of the recording paper wound around the heating roller, and the peeled recording paper comes into contact with the air nozzle. A guide plate is provided for guidance so as not to. Further, when low-temperature compressed air hits the high-temperature recording paper that has just been fixed, gloss unevenness may occur. Therefore, a heater is provided in the air nozzle and the compressed air is jetted in a heated state.

  However, only by providing a heater in the air nozzle, only the compressed air stored near the air nozzle before injection is heated, and the compressed air stored in the back away from the heater is not heated. In this document, it is described that the compressed air is allowed to flow only once for a short time (for example, 0.01 to 0.1 sec) or intermittently with a certain time interval. In the case of feeding only one sheet, heated compressed air can be used, but there are many cases where the recording sheet cannot be peeled off unless it is ejected intermittently. When continuously feeding sheets of recording paper, low-temperature compressed air stored in the back is also jetted, and it is difficult to reliably prevent gloss unevenness. Therefore, a large-capacity heater is required to continuously heat the compressed air flowing during injection.

  Moreover, in order to reliably separate the recording paper, it is necessary to provide at least about a plurality of air nozzles in the width direction of the recording paper. When a large-capacity heater is provided for each of the plurality of air nozzles, Therefore, there is a problem in that the apparatus becomes large and the cost increases.

  The present invention has been made in view of such a problem, and it is possible to heat a large volume of compressed air without providing a dedicated heater or power source for heating the compressed air, thereby reliably preventing uneven gloss after fixing. It is an object of the present invention to propose a fixing device and an image forming apparatus that can prevent the increase in size and cost.

  The object is achieved by the invention described below.

  The fixing device according to the present invention includes a heating roller heated by a predetermined heating member, a pressure roller that presses the heating roller, and a discharge side of a nip portion formed by the heating roller and the pressure roller. In a fixing device that is disposed and has an air jetting unit that jets compressed air from an air nozzle to the leading end of the recording paper that has passed through the nip, and peels the recording paper from the heating roller. A part of the flow path to flow is arranged at a position where heat of the heating member is transmitted by heat conduction or heat radiation.

  The fixing device according to the present invention includes a heating roller heated by a predetermined heating member, a fixing roller, an endless fixing belt stretched around the heating roller and the fixing roller and driven to circulate, and the fixing belt And a pressure roller that presses the fixing roller via the fixing belt, and a paper discharge side of a nip formed by the fixing belt and the pressure roller, and an air nozzle at the leading end of the recording paper that has passed through the nip And a jetting device for jetting compressed air from the fixing belt to release the recording paper from the fixing belt, and the heat of the heating member heats a part of the flow path through which the compressed air flows to the air nozzle. It is arranged at a position transmitted by conduction or thermal radiation.

  According to the fixing device and the image forming apparatus of the present invention, in the fixing device that squeezes the recording paper from the heating roller or the fixing belt by jetting compressed air from the air nozzle to the leading end portion of the recording paper that has passed through the nip portion, the air nozzle is compressed. Since part of the flow path for flowing air is arranged at a position where the heat of the heating member that heats the heating roller is transmitted by heat conduction or heat radiation, there is no need to provide a dedicated heater or power source for heating compressed air Since a large volume of compressed air can be heated, uneven gloss after fixing can be reliably prevented, and an increase in size and cost of the apparatus can be avoided.

  Embodiments relating to the fixing device of the present invention will be described in detail with reference to the drawings.

  First, an image forming apparatus having a fixing device of the present invention will be described with reference to the basic configuration diagram of FIG.

  In FIG. 1, reference numeral 1 denotes a photosensitive drum which is an electrophotographic photosensitive member. The photosensitive drum 1 is rotationally driven in a direction indicated by an arrow at a predetermined peripheral speed, and a surface of the photosensitive drum 1 is negatively charged by a charger 2. Uniformly charged to VH.

  An exposure device 3 outputs a laser beam modulated in accordance with a time-series digital pixel signal of image information input from an image reading device (not shown), a computer, or the like. The uniformly charged surface of the photosensitive drum 1 is scanned and exposed by this laser beam. As a result, the absolute value of the potential of the exposed portion of the photosensitive drum 1 decreases to become the potential VL, and an electrostatic latent image is formed on the surface of the photosensitive drum 1.

  The developing device 4 includes a developing roller 4a that is rotationally driven. The developing roller 4a is disposed opposite to the photosensitive drum 1, and a thin layer of negatively charged toner is formed on the outer peripheral surface thereof. A developing bias voltage whose absolute value is smaller than the potential VH of the photosensitive drum 1 and larger than the potential VL is applied to the developing roller 4a, whereby the toner on the developing roller 4a becomes the potential of the photosensitive drum 1. Reversal development is performed only on the VL portion, and a toner image is formed.

  On the other hand, the recording paper P, which is a transfer material fed from a paper feed unit (not shown), passes through the registration roller 61 and is synchronized with the photosensitive drum 1 and the charged transfer pole 5 at an appropriate timing synchronized with the rotation of the photosensitive drum 1. To the transfer area formed in The toner image on the photosensitive drum 1 is transferred to the recording paper P by the charged transfer pole 5 to which a transfer bias is applied.

  Reference numeral 62 denotes a fixing guide. The recording paper P onto which the toner image has been transferred is conveyed to the fixing device 7 and the toner image transferred onto the recording paper P is fixed. The recording paper P that has passed through the fixing device 7 and has been fixed with the toner image is discharged onto a paper discharge tray (not shown).

  On the other hand, the photosensitive drum 1 from which the recording paper P has been separated is removed by the cleaning device 9 to remove transfer residue toner and the like adhering to the surface thereof, and the cleaned photosensitive drum 1 is repeatedly subjected to the next image formation. To be served.

  Although the above-described image forming apparatus is an apparatus that forms a monochrome image, the present invention is also applied to an apparatus that forms a color image.

  Next, the fixing device 7 according to the present invention will be described in detail based on the sectional view of FIG.

  In FIG. 2, the fixing device 7 includes a heating roller 71 heated by a halogen heater H (heating member), a pressure roller 72 for pressing the heating roller 71 from below, and the like.

  The heating roller 71 is formed of a halogen heater H built in the center, a cored bar 71a formed in a cylindrical shape by aluminum or iron, and a fluororesin such as PFA (perfluoroalkoxy) or PTFE (polytetrafluoroethylene). And a release layer 71b that coats or coats the cored bar 71a with a tube.

  The pressure roller 72 is formed of a core metal 72a formed of a stainless steel or the like, an elastic layer 72b made of a foam of silicon rubber and positioned on the outer peripheral surface of the core metal 72a, a PFA tube, and the like. And a release layer 72c covering the outer peripheral surface of 72b. The pressure roller 72 is urged by a urging member (not shown) to press the heating roller 71 from below.

  In some cases, an induction heating method may be used in place of the halogen heater H as a heating member for heating the heating roller 71.

  Further, a cleaning means 75 for cleaning toner adhering to the heating roller 71 is provided, and a web 75a, a former winding shaft 75b for winding the web 75a before use, and a pressure roller 75c for pressing the web 75a to the heating roller 71 ( A hollow roller) and a winding shaft 75d for winding the web 75a after use. The web 75a is made of a non-woven fabric and is wound up intermittently every predetermined number of sheets.

  With the above configuration, when the heating roller 71 heated by the halogen heater H and driven by a motor (not shown) rotates in the clockwise direction, the pressure roller 72 rotates in the counterclockwise direction. Accordingly, the recording paper P on which the toner image is formed by the image forming apparatus as shown in FIG. 1 is sandwiched and conveyed by the nip portion N formed by the heating roller 71 and the pressure roller 72, and is heated and pressurized. As a result, the toner image on the recording paper P is fixed.

  Here, the toner image on the recording paper P is pressed against the surface of the heating roller 71, and the recording paper P is prevented from being wrapped around the heating roller 71 due to the adhesiveness of the softened toner. Air jetting means for jetting the compressed air and peeling the leading end of the recording paper P wound around the heating roller 71 by the wind pressure of the air is provided, and the air nozzle 81 for jetting the compressed air discharges the recording paper P to the nip N. On the side.

  When the recording paper P passes through the nip portion N, compressed air is ejected from the air nozzle 81, and the leading end of the recording paper P wound around the heating roller 71 is peeled off from the heating roller 71. Since the guide member 79 is provided so as to protrude from the air nozzle 81 toward the nip portion N, the separated recording paper P is conveyed along the guide member 79 without coming into contact with the air nozzle 81. Therefore, the time for injecting the compressed air from the air nozzle 81 may be short, and it may be either continuous injection or intermittent injection in pulses.

  Since the recording paper P is in sliding contact with the guide member 79, it is desirable that the sliding contact surface of the guide member 79 is formed as a smooth surface and a release layer is applied.

  Further, when low-temperature compressed air hits the high-temperature recording paper P that has just been fixed, gloss unevenness may occur, so it is necessary to inject heated high-temperature compressed air. An example of a configuration for heating the compressed air in this way will be described with reference to FIGS. 3 is a perspective view of an air heating roller or the like for heating the compressed air, FIG. 4 is a cross-sectional view of the air heating roller, and FIG. 5 is a schematic diagram showing the entire configuration of the air injection means.

  In FIG. 3, a heating roller 71, a pressure roller 72, and a pressure roller 75c are equivalent to the members described with reference to FIG. Here, a hollow pressure roller 75c formed of a metal such as aluminum is used as a part of a flow path for flowing the compressed air to the air nozzle 81 for injecting the compressed air, and the compressed air is caused to flow inside the pressure roller 75c. Yes.

  Reference numeral 82 denotes an electromagnetic valve for timing the injection from the air nozzle 81.

  The pressure roller 75c configured as described above will be described with reference to FIG.

  At both ends of the pressure roller 75 c, a sleeve 77 is implanted in the holding plate 76, and both inner ends of the pressure roller 75 c are fitted into bearings 78 inserted into the sleeve 77. The holding plate 76 is biased by a biasing member (not shown). Accordingly, the pressure roller 75c is configured to be rotatable and presses the web 75a to the heating roller 71.

  Further, a connecting pipe 83 connected to the electromagnetic valve 82 is inserted into one sleeve 77, and a connecting pipe 84 connected to an air tank for storing compressed air is inserted into the other sleeve 77. The connecting pipes 83 and 84 are made of rubber or plastic.

  Here, since the pressure roller 75c presses the heating roller 71 via the web 75a, the heat of the heating roller 71 heated by the halogen heater H is transmitted to the pressure roller 75c and the pressure roller 75c is heated. When not spraying from the air nozzle 81, the compressed air stored in the inside 75c1 of the pressure roller 75c is heated.

  Accordingly, when the leading end portion of the recording paper P wound around the heating roller 71 is peeled off from the heating roller 71, compressed air heated by the air nozzle 81 can be jetted, so that uneven glossiness is generated on the recording paper P after fixing. It does not occur. Further, since a large amount of compressed air stored in the inside 75c1 of the pressure roller 75c can be heated, it is possible to continue to spray the heated compressed air even when a large number of recording sheets are continuously fed. It is. Furthermore, since a dedicated heater or a power source for heating the compressed air is not necessary, it is possible to avoid an increase in size and cost of the apparatus.

  Next, the entire configuration of the air injection device will be described based on the schematic diagram of FIG.

  The compressed air sent from the air pump 87 is adjusted in pressure by the regulator 86 and then stored in the air tank 85. A part of the compressed air reaches the pressure roller 75c and is heated as described above. When the recording paper P passes through the nip portion N, the electromagnetic valve 82 is opened and compressed air is ejected from the air nozzle 81.

  The number of air nozzles 81 is preferably about 3 to 6 in the longitudinal direction of the heating roller 71, and the number of electromagnetic valves 82 is required to be equal to the number of air nozzles 81.

  Further, without providing the plurality of solenoid valves 82, only one solenoid valve 82 may be arranged upstream of the branch portion 83 a that branches into the plurality of air nozzles 81.

  In addition, in the above embodiment, the compressed air is heated by passing through the pressure roller 75c of the cleaning means 75. However, a dedicated hollow roller that directly presses the heating roller 71 separately from the pressure roller 75c of the cleaning means 75 is provided. It may be provided and heated by flowing compressed air in the hollow roller.

  Further, the pressure roller 75c described above has a configuration in which the outer surface of the high-temperature heating roller 71 is pressed and heated by heat conduction. However, a dedicated hollow roller for allowing the compressed air to flow is disposed in a gap between the halogen heater H in the heating roller 71 and the inner peripheral surface of the heating roller 71, and the roller is heated by heat radiation from the halogen heater H. You may comprise.

  FIG. 6 shows the fixing device configured as described above. The members having the same reference numerals as those in FIG. 2 are the same members as those in FIG.

  In FIG. 6, a metal hollow roller 175 is disposed in a gap between the halogen heater H in the heating roller 71 and the inner peripheral surface of the heating roller 71, and the hollow roller 175 is heated by heat radiation from the halogen heater H. Therefore, the compressed air in the hollow roller 175 is also heated. In this case, since the compressed air does not flow to the pressure roller 75c of the cleaning means 75, the pressure roller 75c does not need to be hollow.

  The fixing device described above is a heat roller fixing type fixing device, but the present invention can also be applied to a belt fixing type fixing device. An example of a belt fixing type fixing device using the present invention will be described below with reference to FIG.

  The fixing belt 101 is formed in an endless shape. For example, a heat-resistant resin belt made of PI (polyimide) or the like is used as a base, the outer peripheral surface of the base is covered with heat-resistant silicon rubber, and further, as a release layer. It is covered with a PFA (perfluoroalkoxy) tube.

  The heating roller 102 has a built-in halogen heater H1 as a heating member for heating the fixing belt 101. For example, the outer peripheral surface of a cylindrical hollow rotating body 102a formed of aluminum or the like is covered with a heat-resistant PFA tube 102b. And it is configured as a hard roller.

  The fixing roller 103 is configured as a soft roller by covering a solid core metal 103a formed of a metal such as iron with a heat-resistant silicone rubber 103b and further covering with a sponge 103c.

  The pressure roller 104 incorporates a halogen heater H2, and covers the outer peripheral surface of a cylindrical hollow rotating body 104a made of, for example, aluminum or the like with a heat-resistant silicon rubber 104b. Fluoroalkoxy) is covered with a tube 104c and configured as a soft roller.

  Note that any heating member may be used as a heating member for heating the fixing belt 101, and for example, an induction heating heating element using an exciting coil may be used. Further, the heating member is not necessarily arranged in the heating roller 102 or the like, and may be arranged anywhere.

  Further, a cleaning unit 105 for cleaning toner and the like adhering to the fixing belt 101 is provided, and the web 105 a, the original winding shaft 105 b for winding the web 105 a before use, and the web 105 a are pressure-bonded to the fixing belt 101 on the heating roller 102. It comprises a pressure roller 105c (hollow roller) to be wound, and a winding shaft 105d for winding the used web 105a. The web 105a is made of a non-woven fabric and is wound up intermittently for every predetermined number of sheets.

  In the above configuration, when the fixing roller 103 is rotated clockwise by a driving unit (not shown), the fixing belt 101 and the heating roller 102 are rotated clockwise, and the pressure roller 104 is rotated counterclockwise. Further, since the heating roller 102 can be heated by the halogen heater H1, the fixing belt 101 in contact with the heating roller 102 is also heated, and the pressure roller 104 is also heated by the halogen heater H2. Since the pressure roller 104 is urged in the direction of the fixing roller 103 by an urging means (not shown), a nip portion N between the fixing belt 101 wound around the fixing roller 103 and the pressure roller 104. Thus, the fed recording paper P is heated and pressurized, and the toner image on the recording paper P is fixed.

  Further, an air nozzle 111 for injecting compressed air is provided on the paper discharge side of the recording paper P with respect to the nip portion N, and the separated recording paper P is guided by a guide member 112 protruding in the direction of the nip portion N from the air nozzle 111 and discharged. Paper.

  Since the compressed air flows into the pressure roller 105c as in the heat roller fixing type fixing device of FIG. 2, the heat of the heating roller 102 heated by the halogen heater H1 passes through the fixing belt 101 and the pressure roller 105c. The compressed air inside the pressure roller 105c is heated. Accordingly, when the leading end portion of the recording paper P wound around the fixing belt 101 at the nip portion N is peeled off from the fixing belt 101, the compressed air heated by the pressure roller 105c can be ejected from the air nozzle 111. There is no occurrence of uneven gloss on the subsequent recording paper P.

  In addition to the pressure roller 105c of the cleaning unit 105, a dedicated hollow roller that is pressure-bonded to the heating roller 102 via the fixing belt 101 may be provided, and the compressed air may flow in the hollow roller to be heated.

  Further, as in FIG. 6, a dedicated hollow roller is arranged in the gap between the halogen heater H1 in the heating roller 102 and the inner peripheral surface of the heating roller 102, and the hollow roller is heated by heat radiation from the halogen heater H1. You may comprise.

  In each of the above embodiments, the temperature at which the compressed air is heated in the roller is preferably between 100 ° C. and the fixing temperature. The fixing temperature is 160 ° C. to 200 ° C.

1 is a basic configuration diagram of an image forming apparatus. FIG. 3 is a cross-sectional view of a fixing device. It is a perspective view, such as an air heating roller which heats compressed air. It is sectional drawing of an air heating roller. It is a schematic diagram which shows the whole structure of an air injection means. It is sectional drawing of the fixing device of another form. It is sectional drawing of a belt fixing apparatus. It is sectional drawing of the fixing device using a peeling nail | claw.

Explanation of symbols

7 Fixing device 71, 102 Heating roller 72, 104 Pressure roller 75, 105 Cleaning means 75a Web 75c, 105c Pressure roller 79, 112 Guide member 81, 111 Air nozzle 82 Solenoid valve 101 Fixing belt 103 Fixing roller 175 Hollow roller H, H1 Halogen heater N Nip part P Recording paper

Claims (10)

A heating roller heated by a predetermined heating member;
A pressure roller for pressing the heating roller;
It is arranged on the paper discharge side of the nip portion formed by the heating roller and the pressure roller, compressed air is jetted from the air nozzle to the leading end of the recording paper that has passed through the nip portion, and the recording paper is removed from the heating roller. In a fixing device comprising an air jetting means for peeling,
A fixing device, wherein a part of a flow path through which compressed air flows to the air nozzle is disposed at a position where heat of the heating member is transmitted by heat conduction or heat radiation. A heating roller heated by a predetermined heating member;
A fixing roller;
An endless fixing belt that is stretched around the heating roller and the fixing roller and is circulated and driven;
A pressure roller for pressing the fixing roller via the fixing belt;
Arranged on the paper discharge side of the nip formed by the fixing belt and the pressure roller, compressed air is jetted from the air nozzle to the leading end of the recording paper that has passed through the nip, and the recording paper is removed from the fixing belt. In a fixing device comprising an air jetting means for peeling,
A fixing device, wherein a part of a flow path through which compressed air flows to the air nozzle is disposed at a position where heat of the heating member is transmitted by heat conduction or heat radiation. 3. The fixing device according to claim 1, wherein compressed air located in a part of the flow path is heated to 100 ° C. or more by the heating member. The fixing device according to claim 1, further comprising a guide member that guides the separated recording paper so as not to contact the air nozzle. The fixing device according to claim 1, wherein a part of the flow path is formed by a metal hollow roller. The fixing device according to claim 5, wherein the hollow roller is in pressure contact with an outer peripheral surface of the heating roller. The fixing device according to claim 5, wherein the hollow roller presses an outer peripheral surface of the heating roller via a web for cleaning the fixing belt. The fixing device according to claim 5, wherein the hollow roller presses an outer peripheral surface of the heating roller via the fixing belt. The fixing device according to claim 5, wherein the hollow roller is disposed in a gap between the heating member built in the heating roller and an inner peripheral surface of the heating roller. An image forming apparatus comprising the fixing device according to claim 1.

Images