JP2007240920A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing the occurrence of a temperature difference on the outer peripheral surface of a fixing roller when continuously carrying and fixing recording materials, and then, preventing the occurrence of uneven glossiness on the recording paper to be succeedingly fixed. <P>SOLUTION: Regarding the image forming apparatus including a fixing device for fixing a toner image on the recording material by heating and pressurizing the recording material with the toner image formed at a nip part formed by a fixing member and a pressurizing member, the image forming apparatus also includes: a compressed air injecting means for injecting compressed air to the leading end of the recording material that has just passed through the nip part so as to peel the recording material from the fixing member; and a control means for controlling the compressed air injecting means to continuously inject the compressed air to the outer peripheral surface of the fixing member lying between the precedingly and succeedingly carried recording materials when continuously carrying the recording materials and fixing the image to the recording material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, when recording material is continuously conveyed and fixed, compressed air is used to uniform the temperature of the outer peripheral surface of the fixing member of the fixing device, thereby preventing gloss unevenness of the recording material after fixing. Relates to the device.

  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 onto which a toner image is transferred is sandwiched between a fixing roller having a built-in halogen heater and a pressure roller that presses the fixing 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, when the recording paper comes into contact with the fixing roller, the heat of the fixing roller is taken away by the low-temperature recording paper, and the temperature of the outer peripheral surface of the fixing roller is lowered. Therefore, when the recording paper is continuously conveyed and fixed, the temperature of the outer peripheral surface of the fixing roller where the recording paper comes into contact decreases, and the fixing roller does not come into contact with the recording paper before and after being conveyed. Since the temperature of the outer peripheral surface of the fixing roller does not decrease, a temperature difference occurs on the outer peripheral surface of the fixing roller. When the recording paper is next fixed in a state where such a temperature difference occurs in the fixing roller, a portion having a different fixing temperature is generated on one recording paper, and the portion fixed at a high temperature has a high glossiness. A portion fixed at a low temperature has a low glossiness and uneven glossiness.

For the purpose of preventing the occurrence of uneven gloss on the recording sheet after fixing due to a temperature difference in the outer peripheral surface of the fixing roller due to the first rotation and the second rotation of the fixing roller, A fixing device that heats the fixing roller using an auxiliary heater at the timing when one round is completed is known (Patent Document 1).
JP-A-9-190112

  As described in Japanese Patent Application Laid-Open No. 2004-260, actually, regarding the problem that a temperature difference occurs on the outer peripheral surface of the fixing roller between the first and second rotations of the fixing roller and uneven glossiness occurs on the recording paper after fixing, Since the temperature rises to some extent while the part of the outer peripheral surface where the temperature has decreased, a clear gloss unevenness does not always occur at the joint between the first and second rounds and is often not very noticeable.

  However, when the recording material is continuously conveyed and fixed, the temperature of the outer peripheral surface of the fixing roller as described above where the recording paper comes into contact decreases, and the recording paper contacts between the recording paper before and after being conveyed. With respect to the problem that gloss unevenness occurs on the recording paper to be fixed next, due to a temperature difference in the outer peripheral surface of the fixing roller without lowering the temperature of the outer peripheral surface of the fixing roller. It cannot be solved.

  The present invention has been made in view of such a problem, and when the recording material is continuously conveyed and fixed, the temperature of the outer peripheral surface of the fixing roller with which the recording paper comes into contact decreases, and the recording paper before and after being conveyed. The temperature of the outer peripheral surface of the fixing roller that does not come into contact with the recording paper does not decrease in temperature and prevents a temperature difference from occurring on the outer peripheral surface of the fixing roller. It is an object of the present invention to propose an image forming apparatus that does not generate such a problem.

  The object is achieved by the invention described below.

  An image forming apparatus according to the present invention includes a fixing device that fixes a toner image to a recording material by heating and pressing a recording material on which the toner image is formed at a nip formed by a fixing member and a pressure member. In the image forming apparatus, the compressed air is ejected to the leading end of the recording material immediately after passing through the nip portion, and the recording material is continuously conveyed by the compressed air ejecting means for separating the recording material from the fixing member. Control means for controlling the compressed air to be continuously ejected from the compressed air ejecting means to the outer peripheral surface of the fixing member corresponding to the space between the recording material before and after being conveyed. It is characterized by.

  According to the image forming apparatus of the present invention, when the recording material is continuously conveyed and fixed, the compressed air is jetted onto the outer peripheral surface of the corresponding fixing member between the recording materials before and after being conveyed. Since the temperature of the outer peripheral surface is made uniform, there is an effect that gloss unevenness does not occur in the recording material to be fixed next.

  Embodiments of the image forming apparatus according to the present invention will be described below with reference to the drawings.

  First, an example of an image forming apparatus will be described based on the configuration diagram of FIG.

  The image forming apparatus includes an image forming apparatus main body GH and an image reading apparatus YS.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus, and a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 6, a sheet feeding and conveying unit, a fixing device 9, and the like. Consists of.

  An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202, and the line image sensor CCD is scanned. Is read.

  A signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 8Y are arranged around the photosensitive drum 1Y. The image forming unit 10M that forms a magenta (M) color image includes a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 8M around the photosensitive drum 1M. In the image forming unit 10C that forms a cyan (C) color image, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 8C are arranged around the photosensitive drum 1C. In the image forming unit 10K that forms a black (K) image, a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 8K are arranged around the photosensitive drum 1K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure device 3C, and the charging unit 2K and the exposure device 3K constitute a latent image forming unit.

  The developing units 4Y, 4M, 4C, and 4K include a two-component developer composed of a toner having a small particle size of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier.

  The intermediate transfer body 6 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 9 fixes the toner image on the recording paper (recording material) P by heating and pressing at a nip portion formed between the heated fixing roller 91 and the pressure roller 92.

  Thus, each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C, and 7K (primary transfer). A toner image synthesized with a color image is formed. The recording paper P stored in the paper feeding cassette 20 is fed by the paper feeding means 21 and is conveyed to the transfer means 7A via the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, etc. A color image is transferred onto P (secondary transfer). The recording paper P to which the color image has been transferred is heated and pressurized by the fixing device 9 and the color toner image on the recording paper P is fixed. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the transfer means 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 from which the recording paper P is separated by curvature.

  The image forming apparatus for forming a color image has been described above. However, an image forming apparatus for forming a monochrome image may be used, or an intermediate transfer member may or may not be used.

  Next, the fixing device according to the present invention will be described with reference to the sectional view of FIG.

  In FIG. 2, the fixing device 9 includes a fixing roller 91 (fixing member) heated by a halogen heater H, a pressure roller 92 (pressure member) that presses the fixing roller 91 from below.

  The fixing roller 91 includes a halogen heater H built in the center, a cored bar 91A formed in a cylindrical shape with aluminum, iron, or the like, a heat-resistant elastic layer 91B formed of silicone rubber, fluorine rubber, or the like, and PFA ( The release layer 91C is made of a fluororesin such as perfluoroalkoxy) or PTFE (polytetrafluoroethylene) and covers the elastic layer 91B with a coating or a tube.

  The pressure roller 92 is formed of a core metal 92A formed of a stainless steel or the like, an elastic layer 92B made of a foam of silicon rubber and positioned on the outer peripheral surface of the core metal 92A, a PFA tube, and the like. It is comprised from the mold release layer 92C which coat | covers the outer peripheral surface of 92B. The pressure roller 92 is urged by a urging member (not shown) to press the fixing roller 91 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 fixing roller 91.

  Further, a cleaning unit 95 for cleaning toner or the like adhering to the fixing roller 91 is provided. The web 95A, a former winding shaft 95B for winding the web 95A before use, and a pressure roller 95C for pressing the web 95A to the fixing roller 91, And a winding shaft 95D for winding the web 95A after use. The web 95A is made of a non-woven fabric and is wound up intermittently every predetermined number of sheets.

  With the above configuration, when the fixing roller 91 heated by the halogen heater H and driven by a motor (not shown) rotates in the clockwise direction, the pressure roller 92 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 fixing roller 91 and the pressure roller 92, and is heated and pressurized. As a result, the toner image on the recording paper P is fixed.

  Here, compressed air ejecting means for ejecting compressed air is provided, and the air nozzle 101 is arranged on the paper discharge side of the recording paper P with respect to the nip portion N.

  As shown in FIG. 3, the air nozzle 101 has a horizontally long opening 101 </ b> A through which compressed air is jetted, and the length in the width direction is larger than the length in the axial direction of the fixing roller 91 and the pressure roller 92. Therefore, even if the recording paper has the maximum size, the compressed air can be ejected over the entire region in the width direction.

  In order to prevent the toner image on the recording paper P from being pressed onto the surface of the fixing roller 91 and preventing the recording paper P from being wound around the fixing roller 91 due to the adhesiveness of the softened toner, the recording paper P is in the nip portion N. , Compressed air is ejected from the opening 101A of the air nozzle 101, and the leading end of the recording paper P wound around the fixing roller 91 is peeled off from the fixing roller 91 by the wind pressure of the compressed air. If the recording paper P is peeled off, the jet of compressed air is stopped.

  Further, since the guide member 96 is provided so as to protrude from the air nozzle 101 toward the nip portion N, the separated recording paper P is conveyed along the guide member 96 without contacting the air nozzle 101.

  Since the recording paper P is in sliding contact with the guide member 96, it is desirable that the sliding contact surface of the guide member 96 is formed as a smooth surface and a release layer is applied.

  Further, when the recording paper P is continuously fixed using such a fixing device 9, the temperature of the outer peripheral surface of the fixing roller 91 with which the recording paper P comes into contact decreases, and the space between the recording paper P before and after being conveyed is reduced. Therefore, the temperature of the outer peripheral surface of the fixing roller 91 that does not come into contact with the recording paper P does not decrease, and a temperature difference occurs in the outer peripheral surface of the fixing roller 91, and gloss unevenness may occur in the recording paper P to be fixed next. Therefore, if the compressed air is sprayed from the air nozzle 101 to the outer peripheral surface of the fixing roller 91 where the recording paper P does not come into contact and the temperature does not decrease, the temperature of the outer peripheral surface of the fixing roller 91 is made uniform. Therefore, it is possible to prevent uneven glossiness from occurring on the recording paper to be fixed next.

  Note that when separating the recording paper P, it is necessary to increase the jet pressure of the compressed air. However, when the temperature of the outer peripheral surface of the fixing roller 91 is made uniform, the jet pressure may be low and the temperature of the outer peripheral surface of the fixing roller 91. The jetting pressure when making the pressure uniform may be about 1/3 to 1/10 of the jetting pressure when separating the recording paper P.

  Further, in order to prevent the compressed air injected from the air nozzle 101 from bouncing back and lowering the temperature of unnecessary portions, as shown in FIG. 2, a regulating member 101B for regulating the injection direction of the compressed air is provided. It is desirable to provide it.

  Next, the configuration for injecting the compressed air will be described based on the flowchart of FIG. 4, the block diagram of FIG. 5, and the drawing showing the steps of conveying the recording paper of FIG.

  When the image formation is started by the operation of the operator and the feeding of the recording paper is started (S1), when the paper feeding sensor 111 arranged on the upstream side of the fixing device 9 detects the passing of the leading edge of the recording paper P (S2). ), The control unit 110 causes the timer 113 to start measuring time (S3), and the timer 113 counts the time t1 until the leading end of the recording paper P passes through the nip N of the fixing device 9. Since this time t1 is constant, if the time t1 has elapsed (Y in S4), the control means 110 opens the control valve 102 consisting of an electromagnetic valve or the like so that compressed air having a pressure higher than that of the air nozzle 101 is applied to the nip portion N. (S5), the leading edge of the recording paper P wound around the fixing roller 91 is peeled off from the fixing roller 91. And after spraying high pressure compressed air for 0.05 second-0.1 second, injection is stopped (S6). This is the state of FIG.

  Next, when the paper discharge sensor 112 that is disposed downstream of the fixing device 9 and detects that the peeled recording paper P has passed, detects the passage of the leading edge of the recording paper P (S7), the control means 110 The timer 113 is started to measure time (S8). Since the control unit 110 can detect the size of the recording paper P loaded in the paper feed cassette 20 by the recording paper size sensor 114, after the recording paper P is detected by the paper discharge sensor 112, The time t2 until the end part passes through the nip part N can be calculated in advance. If this time t2 has elapsed (Y in S9), the control valve 102 is immediately opened to a small pressure, and the air nozzle 101 is compressed at a lower pressure. Air is jetted (S10), and the temperature of the outer peripheral surface of the fixing roller 91 is lowered. This is the state of FIG.

  Since the control unit 110 stores the interval d between the recording paper P before and after continuous feeding, the time t3 until the leading edge of the next recording paper P reaches the nip portion N can be calculated. . Therefore, the control means 110 continuously injects low-pressure compressed air during this time t3. If the time t3 has elapsed (Y in S11) and the paper feed sensor 111 has detected the next recording paper P (Y in S12), the leading edge of the next recording paper P is the nip portion N. Therefore, the pressure of the compressed air is switched to a high pressure (S5), the leading end of the next recording paper P is peeled off from the fixing roller 91, and the above steps are repeated. This is the state of FIG.

  If the paper feed sensor 111 is not detecting the next recording paper P (N in S12), since the continuous paper feed is finished, the jet of compressed air is stopped (S13) and the process is finished.

  In the compressed air injection means, the compressed air is stored in the air tank 103 from the compressor 104 and is injected from the air nozzle 101 when the control valve 102 is opened.

  In addition, the present invention is not limited to the heat roller fixing type fixing device described above, but can be applied to a belt fixing type fixing device as shown in FIG. An example of a belt fixing type fixing device using the present invention will be described below with reference to FIG.

  The fixing belt 201 (fixing member) 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, and the outer peripheral surface of the base is covered with heat-resistant silicon rubber. The release layer is covered with a PFA (perfluoroalkoxy) tube.

  The heating roller 202 incorporates a halogen heater H1 as a heating member for heating the fixing belt 201. For example, the outer peripheral surface of a cylindrical hollow rotating body 202A formed of aluminum or the like is covered with a heat-resistant PFA tube 202B. And it is configured as a hard roller.

  The fixing roller 203 is configured as a soft roller by covering a solid core metal 203A formed of a metal such as iron with a heat-resistant silicone rubber 203B and further covering with a sponge 203C.

  The pressure roller 204 (pressure member) incorporates a halogen heater H2, covers the outer peripheral surface of a cylindrical hollow rotating body 204A made of, for example, aluminum or the like with heat-resistant silicon rubber 204B, and further releases the mold. The layer is covered with a PFA (perfluoroalkoxy) tube 204C and configured as a soft roller.

  Note that any heating member may be used as a heating member for heating the fixing belt 201, 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 202 or the like, and may be arranged anywhere.

  In addition, a cleaning unit 205 for cleaning the toner and the like attached to the fixing belt 201 is provided, and the web 205A, the original winding shaft 205B for winding the web 205A before use, and the web 205A are pressure-bonded to the fixing belt 201 on the heating roller 202. It comprises a pressure roller 205C to be wound and a winding shaft 205D for winding the web 205A after use. The web 205A is made of non-woven fabric and is wound up intermittently every predetermined number of sheets.

  In the above configuration, when the fixing roller 203 is rotated clockwise by a driving unit (not shown), the fixing belt 201 and the heating roller 202 are rotated clockwise, and the pressure roller 204 is rotated counterclockwise. Further, since the heating roller 202 can be heated by the halogen heater H1, the fixing belt 201 in contact with the heating roller 202 is also heated, and the pressure roller 204 is also heated by the halogen heater H2. Since the pressure roller 204 is urged in the direction of the fixing roller 203 by an urging means (not shown), a nip portion N between the fixing belt 201 wound around the fixing roller 203 and the pressure roller 204 is used. Thus, the fed recording paper P is heated and pressurized, and the toner image on the recording paper P is fixed.

  In this case as well, as in the fixing device of the heat roller fixing system in FIG. 2, the compressed air that is ejected from the ejecting portion 101A is provided with the air nozzle 101 that ejects the compressed air on the discharge side of the recording paper P with respect to the nip portion N. After the recording paper P is peeled off, the temperature of the outer peripheral surface of the fixing belt 201 is decreased by jetting compressed air onto the outer peripheral surface of the fixing belt 201 corresponding to the interval between the recording paper P before and after being conveyed. Make uniform.

1 is a configuration diagram of an image forming apparatus. FIG. 3 is a cross-sectional view of a fixing device. It is a perspective view of an air nozzle. It is a flowchart which injects compressed air. It is a block diagram of the member which comprises a compressed air injection apparatus. It is a figure which shows the step in the case of fixing a recording paper continuously. FIG. 4 is a cross-sectional view of a belt fixing type fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 Fixing device 91,203 Fixing roller 202 Heating roller 92,204 Pressure roller 96 Guide member 101 Air nozzle 101B Control member 102 Control valve 110 Control means 111 Paper feed sensor 112 Paper discharge sensor 113 Timer 201 Fixing belt P Recording paper (recording material) )
N Nip part

Claims (5)

An image forming apparatus including a fixing device that fixes a toner image to a recording material by heating and pressing a recording material on which the toner image is formed at a nip formed by a fixing member and a pressure member.
Compressed air jetting means for jetting compressed air to the leading end of the recording material immediately after passing through the nip portion and peeling the recording material from the fixing member;
When the recording material is continuously conveyed and fixed, control is performed so that compressed air is continuously ejected from the compressed air ejecting means to the outer peripheral surface of the corresponding fixing member between the recording materials before and after being conveyed. Control means;
An image forming apparatus comprising: When the recording material is continuously conveyed and fixed, the control means is arranged on the outer peripheral surface of the fixing member corresponding to the leading edge of the recording paper to be fixed next from the trailing edge of the recording material to be fixed. 2. The image forming apparatus according to claim 1, wherein the compressed air is controlled to be continuously ejected by the compressed air ejecting means. When the recording material is peeled off from the fixing member, the control means injects high-pressure compressed air and continuously injects compressed air to the outer peripheral surface of the corresponding fixing member between the recording materials before and after being conveyed. 2. The image forming apparatus according to claim 1, wherein control is performed so as to inject low-pressure compressed air. The image forming apparatus according to any one of claims 1 to 3, wherein a regulating member that regulates a jetting direction of the compressed air is provided in the vicinity of an air nozzle that jets the compressed air in the compressed air jetting unit. . The image forming apparatus according to claim 1, wherein the compressed air ejecting unit ejects the compressed air over an entire region in a width direction orthogonal to the conveyance direction of the recording material.

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