JP2011246224A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device provided with a relay conveyance unit which conveys a recording medium from a transfer unit to a fixing unit by a conveying member whose width is shorter than that of the recording medium, and in which gloss unevenness in the width direction of the recording medium is suppressed.SOLUTION: In the image forming device provided with the relay conveyance unit 75 which conveys transfer paper from the transfer unit toward a fixing entrance guide plate 83 of the fixing unit 80 by surface-moving a conveying belt 76 whose width is shorter than that of the transfer paper, an edge of the fixing entrance guide plate on the relay conveyance unit side is formed so that the part facing the conveying belt forms a recess 83a in the width direction of the transfer paper with respect to the part not facing the conveying belt 76.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.

  2. Description of the Related Art Conventionally, an image forming apparatus has a relay conveyance unit that conveys a recording medium between a transfer unit that transfers a toner image onto the surface of the recording medium and a fixing unit that heats and fixes the toner image on the recording medium. It has been known. As the relay conveyance unit, a recording medium is conveyed by a surface-movable conveyance belt as a conveyance member, and is fed onto a fixing entrance guide plate that guides to a fixing nip portion of the fixing unit. Patent Document 1 describes a relay conveyance unit that conveys a recording medium by providing a plurality of conveyance belts that are shorter than the entire width in the width direction, instead of a conveyance belt corresponding to the entire width of the recording medium. By using a transport belt shorter than the full width, the transport belt can be reduced in size and cost can be reduced.

  In general, in order to stably feed the recording medium from the relay conveyance unit onto the fixing inlet guide plate, the fixing inlet guide plate is disposed close to the relay conveyance unit. Since it is easy to be transmitted to the conveyor belt through the guide plate, the temperature of the conveyor belt rises. On the other hand, in a configuration in which a recording medium is conveyed using a conveyance belt that is shorter than the entire width of the recording medium, there are a region that contacts the conveyance belt and a region that does not contact in the width direction of the recording medium. For this reason, while the recording medium is transported from the transfer unit to the fixing unit, the heat of the transport belt that has risen in temperature is transmitted to the portion of the recording medium that contacts the transport belt, and the temperature between the portion that does not contact the transport belt. It makes a difference. When the recording medium is conveyed to the fixing unit with a temperature difference in the width direction, the amount of heat applied to the toner changes when the toner image is fixed by the fixing unit. If the temperature difference in the width direction is large, the difference in the amount of heat applied to the toner also increases, and the color appearance of the fixed toner image changes, which may appear as uneven gloss in the width direction.

  Such gloss unevenness is particularly noticeable when a toner image having a high glossiness, such as glossy paper or a glossy film, is used, compared to when plain paper is used as the recording medium. In addition, when the temperature inside the machine is low in a low temperature environment, the temperature difference between the area that contacts the conveyor belt and the area that does not contact further increases, and gloss unevenness tends to be noticeable.

  Further, such uneven gloss is a problem that can occur in the same way even if there is only one conveying belt, if the conveying belt is shorter than the entire width in the width direction of the recording medium. Furthermore, not only the conveyance belt but also a conveyance drum or the like is a problem that can occur similarly if the conveyance member is shorter than the entire width in the width direction of the recording medium.

  The present invention has been made in view of the above problems, and an object of the present invention is to form an image including a relay conveyance unit that conveys a recording medium from a transfer unit to a fixing unit by a conveyance member having a width shorter than the entire width of the recording medium. An object of the present invention is to provide an image forming apparatus capable of suppressing uneven glossiness in the width direction of a recording medium.

In order to achieve the above object, the invention of claim 1 includes a transfer unit for transferring a toner image on an image carrier to a recording medium, a fixing nip portion for fixing the toner image on the recording medium by heat, and the recording. A fixing unit having an inlet guide member for guiding the medium to the fixing nip portion and a transport member having a width shorter than the width of the recording medium are moved to move the recording medium from the transfer unit to the inlet guide member of the fixing unit. In the image forming apparatus including the relay transport unit that transports the recording medium, an end of the entrance guide member on the relay transport unit side faces the transport member in the width direction of the recording medium. It is characterized in that it is formed in a concave shape with respect to the portion that is not.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a heat insulating member is provided between the inlet guide member and the transport member.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the heat insulating member is provided in a concave portion of the inlet guide member.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first, second, and third aspects, the outer peripheral surface of the conveying member has a convex rib portion.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first, second, third, and fourth aspects, the relay conveyance unit includes a plurality of conveyance belts as the conveyance member. is there.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the recording medium conveyed by the conveying belt is guided below the conveying surface of the conveying belt in an area where there is no conveying belt in the width direction. A guide member is provided.
According to a seventh aspect of the invention, in the image forming apparatus according to any one of the first, second, third, fourth, fifth and sixth aspects, a cooling means for cooling the conveying member is provided. .
According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, a conveying member temperature detecting means for detecting the temperature of the conveying member is provided, and the cooling means is provided according to a detection result of the conveying member temperature detecting means. It is characterized by operating.
According to a ninth aspect of the present invention, in the image forming apparatus of the eighth aspect, the cooling means is operated when the detection result of the conveying member temperature detecting means is equal to or greater than a predetermined value. is there.
According to a tenth aspect of the present invention, in the image forming apparatus according to the seventh, eighth, or ninth aspect, the image forming apparatus further includes an environmental temperature detection unit that detects an environmental temperature, and a detection result of the environmental temperature detection unit is predetermined. The cooling means is operated when the value is equal to or greater than a predetermined value.
In the present invention, the portion of the inlet guide member facing the conveying member is formed in a concave shape with respect to the portion not facing the conveying member, so that only the gap of the inlet guide member with respect to the conveying member is widened and the inlet guide member is interposed. This makes it difficult to transfer heat from the fixing nip to the conveying member. For this reason, the temperature rise of the conveying member is suppressed, and the temperature difference between the area that contacts the conveying member of the recording medium and the area that does not contact is suppressed while the recording medium is conveyed to the fixing unit. By transporting the recording medium in which the temperature difference in the width direction is suppressed to the fixing unit, the difference in the amount of heat applied to the toner when fixing the toner image with the fixing unit can be reduced, and the width direction of the toner image after fixing Gloss unevenness can be suppressed.

  According to the present invention, in an image forming apparatus including a relay conveyance unit that conveys a recording medium from a transfer unit to a fixing unit by a conveyance member having a width shorter than the width of the recording medium, uneven gloss in the width direction of the recording medium is suppressed. There is an excellent effect that can be done.

1 is a schematic configuration diagram illustrating a configuration of a copier according to an embodiment. 1 is a configuration diagram showing an internal configuration of a printer unit of a copying machine. The block diagram which shows the structure of the process unit for Y and C. The perspective view which shows the structure of a relay conveyance unit and a fixing entrance guide plate. Sectional drawing of the relay conveyance unit and fixing unit in a position with a conveyance belt. The top view which shows the structure of the other example of a relay conveyance unit and a fixing entrance guide plate. The top view which shows the structure of the other example of a fixing entrance guide plate.

  Hereinafter, an electrophotographic copying machine as an image forming apparatus to which the present invention is applied will be described. FIG. 1 is a schematic configuration diagram showing the configuration of the copying machine according to the present embodiment. The copying machine includes a printer unit 1 that forms an image on a transfer sheet P that is a transfer material, a paper feeding device 200 that supplies the transfer sheet P to the printer unit 1, a scanner 300 that reads a document image, and a document that is input to the scanner 300. An automatic document feeder (hereinafter referred to as ADF) 400 is provided.

  The scanner 300 is placed on the contact glass 301 as the first traveling body 303 equipped with a document illumination light source or mirror and the second traveling body 304 equipped with a plurality of reflecting mirrors reciprocate. Scanning of a document (not shown) is performed. The scanning light sent out from the second traveling body 304 is condensed on the imaging surface of the reading sensor 306 installed behind the imaging lens 305 and then read as an image signal by the reading sensor 306.

  On the side surface of the housing of the printer unit 1, a manual feed tray 2 for manually placing the transfer paper P to be fed into the housing, and a paper discharge tray 3 for stacking the image-formed transfer paper P discharged from the housing. Is provided.

  FIG. 2 is a configuration diagram showing the internal configuration of the printer unit. A transfer unit 50 in which an endless intermediate transfer belt 51 is stretched by a plurality of stretching rollers is disposed in the casing of the printer unit 1. The intermediate transfer belt 51 is driven by a driving roller 52, a secondary transfer backup roller 53, a driven roller 54, and four primary transfer rollers 55Y, 55Y, 55K, which are driven to rotate clockwise in FIG. While being stretched, the drive roller 52 is rotated endlessly in the clockwise direction in the drawing. Note that the suffixes Y, C, M, and K attached to the ends of the symbols of the primary transfer roller indicate the members for yellow, cyan, magenta, and black. Hereinafter, the subscripts Y, C, M, and K attached to the ends of the symbols are the same.

  The intermediate transfer belt 51 is greatly curved at the portions where the intermediate transfer belt 51 is wound around the driving roller 52, the secondary transfer backup roller 53, and the driven roller 54, so that the intermediate transfer belt 51 is stretched in an inverted triangular posture with the bottom side directed vertically upward. ing. The belt upper stretch surface corresponding to the base of the inverted triangle extends in the horizontal direction. Above the belt upper stretch surface, four process units 10Y, 10C, 10M, and 10K are provided on the upper stretch surface. It arrange | positions so that it may align with a horizontal direction along the extending direction.

  In FIG. 1 described above, an optical writing unit 68 is disposed above the four process units 10Y, 10C, 10M, and 10K. The optical writing unit 68 emits four writing lights L by driving four semiconductor lasers (not shown) by a laser control unit (not shown) based on the image information of the original read by the scanner 300. Then, the drum-shaped photoconductors 11Y, 11C, 11M, and 11K serving as latent image carriers of the process units 10Y, 10C, 10M, and 10K are scanned in the dark by the writing light L, respectively. , K, electrostatic latent images for Y, C, M, and K are written.

  In this embodiment, the optical writing unit 68 performs optical scanning by deflecting laser light emitted from a semiconductor laser by a polygon mirror (not shown) and reflecting the laser light by a reflection mirror (not shown) or passing through an optical lens. Is used. Instead of such a configuration, an LED array that performs optical scanning may be used.

  FIG. 3 is a configuration diagram showing the configuration of process units for Y and C. The Y process unit 10Y includes a charging member 12Y, a charge eliminating device 13Y, a drum cleaning device 14Y, a developing device 20Y as developing means, a potential sensor 49Y, and the like around a drum-shaped photoconductor 11Y. These are integrally attached to and detached from the printer unit while being held by a casing as a common holding body.

  The charging member 12Y is a roller-like member that is rotatably supported by a bearing (not shown) while being in contact with the photoreceptor 11Y. The surface of the photoconductor 11Y is uniformly charged to the same polarity as, for example, the charge polarity of Y toner by rotating in contact with the photoconductor 11Y while a charging bias is applied by a bias supply means (not shown). Instead of the charging member 12Y having such a configuration, a scorotron charger or the like that performs a uniform charging process on the photoreceptor 11Y in a non-contact manner may be employed.

  A developing device 20Y in which a Y developer containing a magnetic carrier (not shown) and non-magnetic Y toner is contained in a casing 21Y has a developer conveying device 22Y and a developing unit 23Y. In the developing unit 23Y, a developing sleeve 24Y as a developer carrying member that is endlessly moved by being rotated by a driving unit (not shown) exposes a part of its peripheral surface to the outside through an opening provided in the casing 21Y. ing. As a result, a developing region is formed in which the photoconductor 11Y and the developing sleeve 24Y face each other with a predetermined gap.

  Inside the developing sleeve 24Y made of a non-magnetic hollow pipe-like member, a magnet roller (not shown) having a plurality of magnetic poles arranged in the circumferential direction is fixed so as not to rotate with the developing sleeve 24Y. The developing sleeve 24Y is driven to rotate while adsorbing the Y developer in the developer conveying device 22Y, which will be described later, to the surface by the magnetic force generated by the magnet roller, thereby pumping the Y developer from the developer conveying device 22Y. Then, the Y developer conveyed toward the developing area as the developing sleeve 24Y rotates, the doctor blade 25Y having the tip opposed to the surface of the developing sleeve 24Y with a predetermined gap, and the sleeve A doctor gap formed between the surface and the surface is entered. At this time, the layer thickness on the sleeve is regulated to substantially the same thickness as the doctor gap. When the developing sleeve 24Y is rotated and conveyed to the vicinity of the developing area facing the photoconductor 11Y, it receives a magnetic force of a developing magnetic pole (not shown) of the magnet roller and rises on the sleeve to become a magnetic brush. .

  For example, a developing bias having the same polarity as the charging polarity of the toner is applied to the developing sleeve 24Y by a bias supply unit (not shown). As a result, in the development region, non-development in which Y toner is electrostatically moved from the non-image portion side to the sleeve side between the surface of the development sleeve 24Y and the non-image portion (uniformly charged portion = background portion) of the photoreceptor 11Y. Potential acts. Further, a developing potential for electrostatically moving Y toner from the sleeve side toward the electrostatic latent image acts between the surface of the developing sleeve 24Y and the electrostatic latent image on the photoreceptor 11Y. The Y toner in the Y developer is transferred to the electrostatic latent image by the action of the developing potential, so that the electrostatic latent image on the photoreceptor 11Y is developed into the Y toner image.

  The Y developer that has passed through the developing area as the developing sleeve 24Y rotates is separated from the developing sleeve 24Y due to the influence of the repulsive magnetic field formed between the repelling magnetic poles provided in the magnet roller (not shown). The developer returns to the developer conveying device 22Y.

  The developer conveying device 22Y includes two first screw members 26Y, a second screw member 32Y, a partition wall interposed between the two screw members, a toner concentration detection sensor 45Y including a magnetic permeability sensor, and the like. The partition wall divides the first transport chamber, which is a developer transport section, in which the first screw member 26Y is accommodated, and the second transport chamber, which is a developer transport section in which the second screw member 32Y is accommodated. In the region facing both ends in the axial direction of the screw member, both the transfer chambers are communicated with each other through an opening (not shown). The first screw member 26Y and the second screw member 32Y as the agitating / conveying members are respectively provided with a rod-like rotary shaft member whose both ends are rotatably supported by a bearing (not shown), and a spiral projection on the peripheral surface thereof. And a spiral blade. Then, as it is driven to rotate by a driving means (not shown), the Y developer is conveyed in the rotation axis direction by the spiral blade.

  In the first transport chamber in which the first screw member 26Y is accommodated, the Y developer is transported from the near side to the far side in the direction orthogonal to the drawing surface as the first screw member 26Y is driven to rotate. . And if it conveys to the edge part vicinity of the back | inner side of casing 21Y, it will approach into a 2nd conveyance chamber via the opening which is not provided in the partition wall. The above-described developing unit 23Y is formed above the second transfer chamber in which the second screw member 32Y is accommodated, and the second transfer chamber and the developing unit 23Y communicate with each other in the entire area of the opposing part. ing. As a result, the second screw member 32Y and the developing sleeve 24Y disposed obliquely above the second screw member 32Y face each other while maintaining a parallel relationship. In the second transport chamber, the Y developer is transported from the back side to the near side in the direction orthogonal to the drawing sheet as the second screw member 32Y is driven to rotate. In this transport process, the Y developer around the rotation direction of the second screw member 32Y is appropriately pumped up to the developing sleeve 24Y, and the developed Y developer is appropriately collected from the developing sleeve 24Y. Then, the Y developer transported to the vicinity of the near end of the second transport chamber in the drawing returns to the first transport chamber through an opening (not shown) provided in the partition wall.

  A toner concentration detection sensor 45Y as a toner concentration detection means including a magnetic permeability sensor is fixed to the lower wall of the first conveyance chamber, and the toner concentration of the Y developer conveyed by the first screw member 26Y is lowered. And outputs a voltage according to the detection result. A control unit (not shown) replenishes an appropriate amount of Y toner into the first transfer chamber by driving a Y toner supply device (not shown) as necessary based on the output voltage value from the toner concentration detection sensor 45Y. As a result, the toner concentration of the Y developer, which has been lowered with the development, is recovered.

  The Y toner image formed on the photoreceptor 11Y is primarily transferred onto the intermediate transfer belt 51 at a Y primary transfer nip described later. The transfer residual toner that has not been primarily transferred onto the intermediate transfer belt 51 adheres to the surface of the photoreceptor 11Y after passing through the primary transfer process.

  The drum cleaning device 14Y cantilever-supports a cleaning blade 15Y made of, for example, polyurethane rubber, and the free end thereof is brought into contact with the surface of the photoreceptor 11Y. Further, a brush tip end side of a brush roller 16Y having a rotating shaft member that is driven to rotate by a driving means (not shown) and an infinite number of conductive brushes erected on the peripheral surface thereof is brought into contact with the photoreceptor 11Y. Yes. Then, the transfer residual toner described above is scraped off from the surface of the photoreceptor 11Y by the cleaning blade 15Y and the brush roller 16Y. A cleaning bias is applied to the brush roller 16Y via a metal electric field roller 17Y that is in contact with the brush roller 16Y, and the tip of the scraper 18Y is pressed against the electric field roller 17Y. The transfer residual toner scraped off from the photoconductor 11Y by the cleaning blade 15Y and the brush roller 16Y passes through the brush roller 16Y and the electric field roller 17Y, and then is scraped off from the electric field roller 17Y by the scraper 18Y, and then onto the recovery screw 19Y. Fall. Then, after the recovery screw 19Y is driven to rotate, the recovery screw 19Y is discharged out of the casing, and then returned to the developer transport device 22Y via a toner recycling transport means (not shown).

  The surface of the photoreceptor 11Y, from which the transfer residual toner has been cleaned by the drum cleaning device 14Y, is neutralized by the neutralizing device 13Y including a neutralizing lamp and then uniformly charged again by the charging member 14Y.

  Although the Y process unit 10Y has been described in detail, the process units (10C, M, K) of other colors have the same configuration as that of Y except that the color of the toner to be used is different. .

  In FIG. 2 shown above, the photoconductors 11Y, C, M, and K of the process units 10Y, 10C, 10M, and 10K are in contact with the upper stretched surface of the intermediate transfer belt 51 that is endlessly moved in the clockwise direction. Rotating to form primary transfer nips for Y, C, M, and K. On the back side of these primary transfer nips for Y, C, M, and K, the above-described primary transfer rollers 55Y, 55C, 55M, and 55K are in contact with the back surface of the intermediate transfer belt 51. A primary transfer bias having a polarity opposite to the charging polarity of the toner is applied to each of the primary transfer rollers 55Y, 55C, 55M, 55K by a bias supply unit (not shown). Due to this primary transfer bias, a primary transfer electric field is formed in the primary transfer nips for Y, C, M, and K to electrostatically move the toner from the photoreceptor side to the belt side. The Y, C, M, and K toner images formed on the photoreceptors 11Y, 11C, 11M, and 11K are primary for Y, C, M, and K as the photoreceptors 11Y, 11C, 11M, and 11K rotate. When entering the transfer nip, primary transfer is performed by sequentially superimposing on the intermediate transfer belt 51 by the action of the primary transfer electric field and nip pressure. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the front surface (loop outer peripheral surface) of the intermediate transfer belt 51. Instead of the primary transfer rollers 55Y, 55C, 55M, 55K, a conductive brush to which a primary transfer bias is applied, a non-contact type corona charger, or the like may be employed.

  An optical sensor unit 69 is disposed on the right side of the K process unit 10K in the drawing so as to face the front surface of the intermediate transfer belt 51 with a predetermined gap. The optical sensor unit 69 detects a mark (not shown) provided at a predetermined pitch in the belt circumferential direction at one end of the intermediate transfer belt 51 in the belt width direction. The moving speed of the intermediate transfer belt 51 can be measured based on the detection time interval of each mark.

  A secondary transfer roller 56 as an abutting member is disposed below the intermediate transfer belt 51. The secondary transfer roller 56 is rotated counterclockwise in the drawing by a driving means (not shown) while the intermediate transfer belt 51 A secondary transfer nip is formed in contact with the front surface. A secondary transfer backup roller 53 wraps around the intermediate transfer belt 51 on the back side of the secondary transfer nip. A secondary transfer bias having the same polarity as the toner charging polarity is applied to the secondary transfer backup roller 53 by a secondary transfer power source (not shown). On the other hand, the secondary transfer roller 56 that is a contact member that is in contact with the front surface of the belt and forms a secondary transfer nip is grounded. As a result, a secondary transfer electric field is formed between the secondary transfer backup roller 53 and the secondary transfer roller 56. The four-color toner image formed on the front surface of the intermediate transfer belt 51 enters the secondary transfer nip as the intermediate transfer belt 51 moves endlessly.

  In FIG. 1 described above, the paper feeding device 200 is fed with a paper feeding cassette 201 for storing the transfer paper P, and a paper feeding roller 202 for feeding the transfer paper P stored in the paper feeding cassette 201 out of the cassette. A plurality of separation roller pairs 203 for separating the transfer paper P one by one, a plurality of conveyance roller pairs 205 for conveying the separated transfer paper P along the delivery path 204, and the like are provided. The sheet feeding device 200 is disposed directly below the printer unit 1 as shown in the figure. The feeding path 204 of the paper feeding device 200 is connected to the paper feeding path 70 of the printer unit 1. As a result, the transfer paper P sent out from the paper feed cassette 201 of the paper feed device 200 is sent into the paper feed path 70 of the printer unit 1 via the feed path 204.

  Near the end of the paper feed path 70 of the printer unit 1, a registration roller pair 71 is provided, and the transfer paper P sandwiched between the rollers can be synchronized with the four-color toner image on the intermediate transfer belt 51. Feed into the secondary transfer nip. In the secondary transfer nip, the four-color toner images on the intermediate transfer belt 51 are collectively transferred to the transfer paper P due to the influence of the secondary transfer electric field and nip pressure, and combined with the white color of the transfer paper P, Become. The transfer paper P on which the full-color image is formed in this way is separated from the intermediate transfer belt 51 when discharged from the secondary transfer nip.

  The transfer paper P discharged from the secondary transfer nip is conveyed along a secondary transfer outlet guide plate 57 (shown in FIG. 5) to a relay conveyance unit 75 described in detail later. The relay conveyance unit 75 conveys the transfer paper P toward the fixing unit 80.

  Next, the relay conveyance unit 75 and the fixing unit 80 will be described in detail. FIG. 4 is a perspective view illustrating configurations of the relay conveyance unit 75 and the fixing unit 80. As shown in FIG. 4, the relay conveyance unit 75 is endlessly moved in the counterclockwise direction in the drawing while being stretched between the driving roller 77, the driven roller 79 (shown in FIG. 5), and both rollers. Two conveyance belts 76 having a width smaller than the width of the belt are provided. The shaft of the drive roller 77 is fixedly attached to the secondary transfer device side, and is driven from a main body drive system (not shown) via a conveyance drive gear 93. In this relay conveyance unit 75, the upper stretched surface of the conveyance belt 76 becomes the conveyance surface. A sheet suction fan 78 is provided between the driving roller 77 and the driven roller 79 below the conveying belt 76. The transport belt 76 has a plurality of holes 76 a, and the transfer paper P is attracted to the transport belt 76 by the air current of the paper suction fan 78. As a result, the transfer paper P comes into close contact with the conveyance belt 76, and the transfer paper P can be reliably conveyed. FIG. 5 is a cross-sectional view illustrating the configuration of the relay conveyance unit 75 and the fixing unit 80 at a position where the conveyance belt is present in the width direction.

  Further, the relay conveyance unit 75 includes a guide member 92 provided so as to penetrate through the inner peripheral portions of the two conveyance belts 76 in the entire width direction of the transfer paper. The guide member 92 guides the transfer paper P to be transported below the transport surface in an area where the transport belt 76 is not present, thereby stabilizing the transport performance.

  A fixing entrance guide plate 83 serving as an entrance guide member for guiding the transfer sheet P to the fixing nip at a predetermined angle is disposed on the relay conveyance unit 75 side of the fixing unit 80. The transfer paper P conveyed in contact with the conveyance belt 76 of the relay conveyance unit 75 is conveyed toward the fixing nip portion of the fixing unit 80 along the fixing inlet guide plate 83. The fixing nip portion is formed by a heating roller 81 including a heat source such as a halogen lamp (not shown) and a pressure roller 82 pressed toward the heating roller 81. The transfer paper P sandwiched in the fixing nip portion is heated while being pressed, and is sent out of the fixing unit 80 while the full color image is fixed on the surface.

  Here, in the copying machine having the conventional configuration, while the transfer paper P is transported from the secondary transfer device to the fixing unit 80, a portion of the transfer paper P that contacts the transport belt 76 and a portion of the transfer paper P that does not contact the transport belt 76 Temperature difference will occur. This is because the fixing inlet guide plate 83 is formed of a metal material and is likely to be heated to a high temperature by the heat source of the fixing unit 80. Heat is also transferred from the fixing entrance guide plate 83 that has reached a high temperature to the conveying belt 76 disposed in the vicinity, and the conveying belt 76 rises in temperature. While the transfer paper P contacts the transport belt 76 of the relay transport unit and is transported from the secondary transfer device to the fixing unit 80, the portion of the transfer paper P in contact with the transport belt 76 has a temperature rise of the transport belt 76. Heat is transmitted and the temperature rises. On the other hand, the temperature of the guide member 92 disposed close to the fixing entrance guide plate 83 also rises. However, the temperature rise due to the transfer of the heat of the guide member 92 to the transfer paper P in the region opposed to the guide member 92 without the conveyance belt 76. It is considered small. The transfer paper P is guided by being brought into contact with the guide member 92, for example, when the transfer paper P is weak and part of the transfer paper P falls below the transport surface. Is. Furthermore, as shown in FIG. 4, the guide member 92 can further reduce the contact area between the transfer paper P and the guide member 92 by providing a convex rib 92 a on the upper surface. That is, since the transfer paper P does not contact the guide member 92 continuously, it is considered that the temperature rise due to the heat of the guide member 92 being transferred to the transfer paper P is small. As a result, a temperature difference occurs between the portion of the transfer paper P that is in contact with the conveyance belt 76 and the portion that is not in contact.

  When the transfer paper P is conveyed to the fixing unit 80 with a temperature difference in the width direction, the amount of heat applied to the toner changes when the fixing unit 80 fixes the toner image. If the temperature difference in the width direction is large, the difference in the amount of heat applied to the toner also increases, and the color appearance of the fixed toner image changes, which may appear as uneven gloss in the width direction.

  Therefore, in the copying machine according to the present embodiment, the fixing inlet guide plate 83 is shortened in the portion where the conveying belt 76 is present in the width direction, and the end portion of the fixing inlet guide plate 83 on the relay conveying unit 75 side has the conveying belt 76. The portion is formed to be concave 83a with respect to the portion without the conveyor belt 76. Here, as the concave 83a, as shown in FIG. 4, the region facing the conveyor belt 76 is cut out in a rectangular shape, as shown in FIG. 6, the both ends are cut out obliquely, and in FIG. As shown, there are those cut out in an arc shape. By making the shape of the fixing inlet guide plate 83 as described above, the gap between the fixing inlet guide plate 83 and the conveying belt 76 is increased, and as a result, the heat of the fixing nip portion is transferred via the fixing inlet guide plate 83 to the conveying belt. It becomes difficult to be transmitted to 76. For this reason, the temperature rise of the conveyance belt 76 is suppressed, and the temperature rise in the region of the transfer paper P that contacts the conveyance belt 76 that occurs while the transfer paper P is conveyed to the fixing unit 80 is suppressed. Therefore, the temperature difference between the portion of the transfer paper P that contacts the conveyance belt 76 and the portion that does not contact the belt is suppressed. By transferring the transfer sheet P in a state where the temperature difference in the width direction is suppressed to the fixing unit 80, the difference in the amount of heat applied to the toner when the toner image is fixed by the fixing unit 80 can be reduced. Gloss unevenness can be suppressed.

  Further, a heat insulating member 91 is provided to block radiant heat from the fixing inlet guide plate 83 to the conveying belt 76. Thereby, the temperature rise of the conveyance belt 76 is further suppressed, and the temperature difference in the width direction of the transfer paper P is suppressed. The material of the heat insulating member 91 is not particularly limited, but by using an elastic foam, the heat insulating effect of the bubbles of the foam is also helped and the heat insulating performance is improved. At this time, typical embodiments of the elastic foam include foams of urethane resin and silicone resin. Further, as shown in FIG. 5, the heat insulating member 91 may be provided with an uneven surface on the surface so as to reduce the contact area with the fixing entrance guide plate 83. Thereby, a mutual contact area can be reduced, the heat absorbed is reduced, and the heat insulation effect is further improved.

  Furthermore, the conveyance belt 76 is provided with a convex rib 76b orthogonal to the conveyance direction, thereby reducing the contact area between the transfer paper P and the conveyance belt 76, and the heat of the conveyance belt 76 is not easily transmitted to the transfer paper P. is doing.

  In addition, a cooling device is provided below the conveying belt 76 away from the fixing unit 80. The cooling device is formed of a cooling fan 94 and a cylindrical resin duct 95, and the air drawn from the cooling fan 94 is blown onto the conveying belt 76 through the cylindrical resin duct 95, thereby cooling the conveying belt 76. is doing.

  In the present embodiment, a non-contact temperature detection sensor 96 that detects the surface temperature of the conveyor belt 76 is provided, and the cooling fan 94 is operated when the temperature of the conveyor belt 76 exceeds a certain temperature. As for the operation of the cooling fan 94, in addition to this, not only the temperature of the conveyor belt 76 detected by the temperature detection sensor 96 but also an ambient temperature detection sensor for detecting the outside air and the temperature inside the machine, It may be operated when the temperature difference between the temperature of the belt and the conveyor belt exceeds a certain level. This further suppresses the temperature difference between the portion of the transfer paper P that contacts the conveyance belt 76 and the portion that does not contact.

  In the present embodiment, the present invention will be described using the relay conveyance unit 75 having a configuration in which the region of the transfer paper P that does not contact the conveyance belt 76 is guided by the guide member 92 in order to stabilize conveyance. However, it is not limited to this. The same problem occurs in the relay conveyance unit 75 that does not include the guide member 92, and the present invention is applicable.

  In the present embodiment, the present invention has been described using the transport belt 76 as the transport member of the relay transport unit 75, but the present invention is not limited to this. The present invention can also be applied when a transport roller is used as the transport member.

  In this embodiment, the toner image is primarily transferred from the plurality of photosensitive drums 11C, 11M, 11C, and 11K to the intermediate transfer belt 51, and then the toner image is secondarily transferred to the recording medium using the secondary transfer roller 56. Although the present invention has been described using a so-called intermediate transfer type copying machine, the present invention is not limited to this. The present invention is also applicable to a so-called direct transfer type image forming apparatus in which a toner image is transferred from a photosensitive drum to a transfer sheet P using a transfer roller.

As described above, according to the present embodiment, the secondary transfer roller 56 for transferring the toner image to the transfer paper, the fixing unit 80 for fixing the toner image on the transfer paper by heat, and the transport member having a width shorter than the width of the transfer paper. And a transfer conveyance unit 75 that conveys the transfer sheet from the secondary transfer roller 56 toward the fixing inlet guide plate 83 that is an inlet guide member of the fixing unit 80. The end portion of the fixing entrance guide plate 83 on the relay conveyance unit 75 side is formed such that a portion facing the conveyance belt 76 in the width direction of the transfer sheet is concave 83a with respect to a portion not opposed to the conveyance belt 76. As a result, the gap between the fixing inlet guide plate 83 and the conveying belt 76 is widened, and the heat of the fixing nip portion is hardly transmitted to the conveying belt 76 via the fixing inlet guide plate 83. For this reason, the temperature rise of the conveyance belt 76 is suppressed, and the temperature difference between the area where the transfer paper is in contact with the conveyance belt 76 and the area where the transfer paper is not in contact is suppressed while the transfer paper is conveyed to the fixing unit 80. By transferring the transfer paper in a state where the temperature difference in the width direction is suppressed to the fixing unit 80, the difference in the amount of heat applied to the toner when the toner image is fixed by the fixing unit 80 can be reduced. Therefore, gloss unevenness in the width direction of the toner image after fixing can be suppressed.
Further, according to the present embodiment, since the heat insulating member 91 is provided between the fixing inlet guide plate 83 and the conveyance belt 76, heat is hardly transmitted via the fixing inlet guide plate 83. The temperature rise is suppressed, and the temperature difference in the width direction of the transfer paper is suppressed.
In addition, according to the present embodiment, by providing the heat insulating member 91 in the concave portion 83a of the fixing inlet guide plate 83, it is possible to make it difficult to efficiently transfer heat with a space-saving configuration.
Further, according to the present embodiment, by providing the convex rib portion 76b on the outer peripheral surface of the transport belt, the contact area between the transfer paper P and the transport belt 76 is reduced, and the transfer belt P is placed on the transfer paper P. It is possible to suppress the temperature difference in the width direction of the transfer paper P by making it difficult to transmit heat.
In addition, according to the present embodiment, the relay conveyance unit 80 has a plurality of conveyance belts as the conveyance belt 76, so that the conveyance performance can be stabilized.
Further, according to the present embodiment, the relay conveyance unit 80 guides the transfer paper conveyed by the conveyance belt in an area where there is no conveyance belt 76 in the width direction of the transfer paper below the conveyance surface of the conveyance belt 76. A member 92 is provided. As a result, the transportability can be further stabilized.
Further, according to the present embodiment, by providing the cooling fan 94 as a cooling device for cooling the conveyor belt 78, the conveyor belt 76 is cooled to suppress an increase in temperature. Thereby, the temperature difference in the width direction of the transfer paper P is further suppressed.
Further, according to the present embodiment, the temperature detection sensor 96 is provided as a conveyance member temperature detection unit that detects the temperature of the conveyance belt 76, and the cooling fan 94 is provided according to the detection result of the conveyance belt 76 temperature by the temperature detection sensor 96. It is configured to operate. Thereby, the temperature rise of the conveyance belt 76 can be suppressed efficiently.
Further, according to the present embodiment, the configuration in which the cooling fan 94 operates when the temperature detected by the temperature detection sensor 96 exceeds a certain temperature can efficiently suppress the temperature rise of the conveyor belt 76. .
In addition, according to the present embodiment, an environmental temperature detection unit that detects the environmental temperature may be provided, and may be operated when the temperature difference between the environmental temperature and the conveyance belt becomes a certain level or more. This further suppresses the temperature difference between the portion of the transfer paper P that is in contact with the conveyance belt 76 and the portion that is not in contact, and the temperature difference in the width direction of the transfer paper P can be suppressed.

50 Transfer Unit 51 Intermediate Transfer Belt 53 Secondary Transfer Backup Roller 56 Secondary Transfer Roller 57 Transfer Exit Guide Plate 75 Relay Transport Unit 76 Transport Belt 76a Hole 76b Convex Rib 77 Drive Roller 78 Paper Adsorption Fan 79 Followed Roller 80 Fixing Unit 81 Heating roller 82 Pressure roller 83 Fixing entrance guide plate 83a Concave portion 91 Heat insulating member 92 Guide member

JP 2002-002997 A

Claims (10)

Fixing having a transfer unit for transferring a toner image on an image carrier to a recording medium, a fixing nip portion for fixing the toner image on the recording medium by heat, and an inlet guide member for guiding the recording medium to the fixing nip portion In an image forming apparatus comprising: a unit; and a relay conveyance unit that conveys the recording medium from the transfer unit toward an inlet guide member of the fixing unit by moving the surface of a conveyance member that is shorter than the width of the recording medium.
An end portion of the entrance guide member on the relay conveyance unit side is formed in a concave shape with respect to a position where the conveyance member is opposed to the conveyance member in the width direction of the recording medium. Image forming apparatus.   2. The image forming apparatus according to claim 1, wherein a heat insulating member is provided between the inlet guide member and the conveying member.   3. The image forming apparatus according to claim 1, wherein the heat insulating member is provided in a concave portion of the inlet guide member.   4. The image forming apparatus according to claim 1, further comprising a convex rib portion on an outer peripheral surface of the conveying member.   5. The image forming apparatus according to claim 1, wherein the relay transport unit includes a plurality of transport belts as the transport member.   6. The image forming apparatus according to claim 5, further comprising a guide member that guides a recording medium conveyed by the conveyance belt in a region where there is no conveyance belt in the width direction below the conveyance surface of the conveyance belt. Image forming apparatus.   7. The image forming apparatus according to claim 1, further comprising a cooling unit that cools the conveying member.   8. The image forming apparatus according to claim 7, further comprising: a conveying member temperature detecting unit configured to detect a temperature of the conveying member, and operating the cooling unit according to a detection result of the conveying member temperature detecting unit. apparatus.   9. The image forming apparatus according to claim 8, wherein the cooling unit is operated when a detection result of the conveying member temperature detection unit is equal to or greater than a predetermined value.   10. The image forming apparatus according to claim 7, further comprising environmental temperature detection means for detecting an environmental temperature, wherein the cooling means is provided when a detection result of the environmental temperature detection means is equal to or greater than a predetermined value. An image forming apparatus that is operated.

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