JP4596364B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus having the same.

  In general, an image forming apparatus includes a fixing device that fixes a developer image formed on a sheet to the sheet.

  As a fixing device of this type, a nip is formed between a heating roll and a pressure roll pressed against the heating roll, and a sheet on which a developer image is formed is passed through the nip, and the sheet passes through the nip. A pressure roll type is known in which a developer image is heated and pressed during fixing. In addition, as a fixing device of this type, a nip is formed between a heating roll and an endless belt that comes into contact with the heating roll, and a sheet on which a developer image is formed is passed through the nip. A belt type is known in which a developer image is heated and fixed while passing through the belt (for example, Patent Document 1). Further, as a fixing device, two rolls are brought into contact with the heating roll, the sheet is conveyed from the position of one roll to the position of the other roll, and the developer image formed on the sheet is conveyed while being conveyed. There are known ones that perform fixing by heating (for example, Patent Document 2 and Patent Document 3).

JP 2003-302853 A JP-A-55-29822 JP 2003-98874 A

  In a pressure roll type fixing device, in order to widen the nip width for the purpose of transferring sufficient heat to the sheet, a heating roll and a pressure roll that is elastically deformed by being pressed against the heating roll are used. Since the nip is formed, it is necessary to increase the pressing force for pressing the pressure roll, or to make the pressure roll itself have a large diameter. For this reason, there is a problem that the manufacturing cost increases in order to make the device strong enough to withstand the pressure contact force of the pressure roll, or the size of the device increases as the diameter of the pressure roll increases. there were.

  Further, in the belt type fixing device, the number of parts increases due to the complexity of the mechanism, and the manufacturing cost increases, and it is necessary to provide a mechanism for rotatably supporting the belt. There was a problem of becoming.

  Further, in the type of fixing device in which two rolls are brought into contact with the pressure roll, the sheet is in good contact with the heating roll at the position where the pressure roll and each roll come into contact with each other. In the region, the sheet is separated from the heating roll, and there is a problem that heat may not be sufficiently transmitted to the sheet.

  An object of the present invention is to provide a fixing device that solves the above-described problems, and that favorably transfers heat from a heating roll to a sheet while avoiding an increase in manufacturing cost and an increase in size of the device. .

In order to solve the above problems, the present invention is characterized by a heating roll, a first roll that contacts the heating roll to form a first nip, and a second that contacts the heating roll. A second roll forming a nip and guide means for guiding the conveyed sheet , wherein the central axis of the first roll and the central axis of the second roll are more than the central axis of the heating roll. Is also located above in the direction of gravity, heated while conveying the sheet from the first nip to the second nip , and formed on the guide means along the outer shape of the first roll. The fixing device includes a groove and a second groove formed along the outer shape of the second roll . Therefore, while the sheet is conveyed from the first nip to the second nip, the sheet receives gravity in the direction of the heating roll due to its own weight, and comes into contact with the heating roll, and the sheet floats away from the heating roll. It is hard to become. Therefore, the sheet can receive heat conduction well from the heating roll. In addition, by providing the first roll and the second roll, it is not necessary to provide a complicated belt mechanism or a large-diameter pressure roll, and the apparatus can be prevented from becoming large and expensive. In addition, the first roll is covered with the first groove and the second roll is covered with the second groove. Even if a roll having a small heat capacity is used, both rolls are difficult to cool, and thermal efficiency is improved. improves.

  Preferably, the guide means is movable between an open state retracted from the first roll and the second roll and a closed state close to the first roll and the second roll. And supporting means for supporting. Therefore, by opening the guide means, for example, maintenance such as removal of a sheet jammed in the first nip or the second nip can be easily performed.

  The present invention includes an image forming apparatus having the above-described fixing device.

  According to the present invention, it is possible to provide a fixing device in which heat is favorably transferred from a heating roll to a sheet while avoiding an increase in manufacturing cost and an increase in size of the device.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 to be described later is mounted in the image forming apparatus main body 12, and a discharge unit 16 is provided on the upper portion of the image forming apparatus main body 12. In addition, for example, two-stage sheet feeding devices 18 and 18 are disposed below the image forming apparatus main body 12.

  The image forming means 14 is of an electrophotographic system, and is charged by the image carrier 28 made of a photosensitive member, a charging device 30 made of, for example, a charging roll for uniformly charging the image carrier 28, and the charging device 30. An optical writing device 32 that writes a latent image on the image carrier 28 with light, a developing device 34 that visualizes the latent image of the image carrier 28 formed by the optical writing device 32 with a developer, and the developing device 34 A transfer device 36 composed of, for example, a transfer roll for transferring the developer image to the paper, a cleaning device 38 for cleaning the developer remaining on the image carrier 28, and the developer image on the paper transferred by the transfer device 36 on the paper. And a fixing device 40 to be fixed later. The optical writing device 32 is composed of, for example, a scanning laser exposure device, and forms a latent image on the image carrier 28 across a process cartridge 46 described later. The cleaning device 38 includes a cleaning blade 42 that contacts the image carrier 28, and a developer recovery unit 44 that stores the developer scraped off by the cleaning blade 42. The optical writing device 32 may use an LED, a surface emitting laser, or the like as another embodiment.

  Of the members constituting the image forming means 14, the image carrier 28, the charging device 30, the developing device 34 and the cleaning device 38 are integrated as a process cartridge 46 and can be exchanged.

  A sheet feeding device 18 that supplies sheets to the image forming unit 14 includes, for example, a sheet storage unit 20 including a sheet feeding cassette, a pip-up roll 60 that picks up the uppermost sheet stored in the sheet storage unit, and a pip-up It is composed of a feed roll 61 for conveying a sheet picked up by the roll 60 and a separating means 62 for separating and separating the sheets in cooperation with the feed roll 61. Sheets are stored in the sheet storage unit 20 in a stacked state. The separating means 62 may be a roll-shaped one as another embodiment instead of the illustrated plate-shaped one.

  A registration roll 24 is provided downstream of the feed roll 61 in the sheet conveying direction, and the transfer device 36 and the image carrier 28 of the process cartridge 46 are provided on the downstream side of the registration roll 24, respectively. Is provided with the above-described fixing device 40.

In FIG. 2, a fixing device 40 according to an embodiment of the present invention is shown.
The fixing device 40 includes a heating roll 72 provided with a heat source 70 such as a halogen heater, a first roll 74 that contacts the heating roll 72 to form a first nip N1, and a heating roll 72 that contacts the heating roll 72. The second roll 76 that forms the second nip N2, the separation claw 78 that constitutes the separating means provided downstream of the second roll 76 in the rotation direction of the heating roll 72, and at least close to the heating roll 72 The guide member 80 constituting the guide means provided at the position from the first nip N1 to the second nip N2 and a part or all of each member constituting the fixing device 40 are mounted. Frame 82.

  The heating roll 72 includes a cylindrical tubular member 72a made of a metal tube such as aluminum and the heat source 70 described above. The heat source 70 is built in the cylindrical member 72a over substantially the entire area of the heating roll 72 in the axial direction, and heats the cylindrical member 72a. The outer peripheral surface of the cylindrical member 72a is coated with, for example, a fluorine-based resin, and a surface treatment is performed on the outer peripheral surface to make it difficult for the sheet on which the developer image is formed to adhere. The heating roll 72 is rotatably supported by, for example, a frame 82 to be described later, and receives driving transmission from a driving unit (not shown) such as a motor, and rotates in the direction of the arrow shown in FIG. .

  A first roll 74 is provided in contact with the outer peripheral surface of the heating roll 72. The first roll 74 is pressed against the heating roll 72 by a biasing means (not shown) such as a spring to form a nip N1 between the first roll 74 and the heating roll 72, and the first roll 74 is not shown including a bearing or the like. It is rotatably supported by the support means. The first roll 74 is a driven roll that rotates as the heating roll 72 rotates, and a transmission means including a gear that transmits the rotation of the heating roll 72 to the first roll 74 may be provided. However, no special drive transmission means is provided, and a configuration in which drive is transmitted to the first roll by a frictional force generated between the outer peripheral surface of the heating roll 72 and the outer peripheral surface of the first roll 74 is adopted. May be.

  The second roll 76 is in contact with the outer peripheral surface of the heating roll 72 at a position downstream of the heating roll 72 in the rotation direction with respect to the position where the first roll 74 of the heating roll 72 is in contact. The second roll 76 forms a nip N2 with the heating roll 72 and is supported by a support means (not shown) such as a bearing. Also, the second roll 76 is a driven roll that rotates as the heating roll 72 rotates, like the first roll 74.

  As described above, the first roll 74 and the second roll 76 are both driven rolls that receive drive transmission from the heating roll 72, and the circumferences of the first roll 74, the second roll 76, and the heating roll 72. The speed is equal.

  Here, the diameter R 1 of the first roll 74 and the diameter R 2 of the second roll 76 are smaller than the diameter R of the heating roll 72. Accordingly, the two rolls of the first roll 74 and the second roll 76 are arranged around the heating roll 72 while being in contact with the heating roll 72 while being restricted by a certain layout described later. It becomes possible to do. Moreover, since the diameter R1 and the diameter R2 can be made relatively small, the heat capacity of the first roll 74 and the second roll 76 can be made relatively small accordingly. Therefore, from the warm-up time, that is, when the power is turned on, the first roll 74 and the second roll 76 are sufficiently heated by the heat transfer from the heating roll 72, and the developer on the sheet is developed. The time until the image can be fixed by heating can be shortened.

  In this embodiment, the diameter R1 of the first roll 74 and the diameter R2 of the second roll 76 are substantially the same diameter, but the diameter R1 and the diameter R2 may be different values. For example, the diameter R1 of the first roll may be configured to be smaller than the diameter R2 of the second roll.

  Further, the heating roll 72, the first roll 74, and the second roll 76 are such that the central axis of the first roll 74 and the central axis of the second roll 76 are in the direction of gravity more than the central axis of the heating roll 72. It arrange | positions so that it may be located upwards. Here, the center axis corresponds to the center axis if the roll has a rotating shaft and is supported by the rotating shaft, for example. In addition, for example, when the entire outer peripheral portion of each roll is slidably supported by the bearing and the roll does not have a physical rotation axis, a circle formed by the longitudinal section of the roll is formed. The center of is the central axis. Due to such a layout, in the region from the position of the first roll 74 to the position of the second roll 76, the sheet receives gravity in the downward direction, that is, in the direction of the heating roll 72, due to its own weight. It becomes easy to contact 72 well.

  The separation claw 78 that constitutes the separation means is located downstream of the second roll 76 in the rotation direction of the heating roll 72, is formed of, for example, resin, and the front end thereof is in contact with the heating roll 72, and the second nip N2 The sheet that has passed through is separated from the heating roll 72.

  The guide member 80 constituting the guide means is provided in the vicinity of the heating roll 72 and at least at a position between the first nip N1 and the second nip N2. When the sheet that has passed through the first nip N1 is lifted from the heating roll 72, the guide member 80 is located at a position close to the heating roll 72 without being greatly separated from the heating roll 72. Guide you to stay. Further, on the surface of the guide member 80 on the heating roll 72 side, a first groove 80a formed along the outer shape of the first roll 74 and 80b formed along the outer shape of the second roll 76 are formed. And are provided. As a result, the first roll 74 is surrounded by the first groove 80a, and the second roll 76 is surrounded by the second groove 80b. Therefore, the heat radiation from both rolls is satisfactorily suppressed, and the thermal efficiency of the fixing device 40 can be improved.

  As the shape of the guide member 80, the first roll 74, the first roll 74, and the second groove 80b are replaced with the first roll 74 and the second roll 80b while guiding the sheet so as to remain in the vicinity of the heating roll 72. The shape which suppresses the heat radiation from the second roll 76 can be adopted as appropriate.

  Further, the guide member 80 is movable between an open state retracted from the first roll 74 and the second roll 76 and a closed state close to the first roll 74 and the second roll 76. It is supported by the support member 83 which comprises a support means so that it may become. For example, the support member 83 can be configured by a shaft that rotatably supports the guide member 80 with the vicinity of the rear end portion of the guide member 80 in the sheet conveyance direction as a fulcrum. By providing the support member 83, the guide member 80 can be opened. For example, the maintenance work of the apparatus such as removing the sheet jammed in the first nip N1 or the second nip N2 can be performed. It becomes easier to do. In FIG. 2, the guide member 80 in the closed state is shown.

  A heating roll 72, a first roll 74, a second roll 76, and a separation claw 78 that are members constituting the fixing device 40 are attached to the frame 82. The frame 82 is a member to which a part or all of each member constituting the fixing device 40 is attached. If the frame 82 is configured to be detachable from the image forming apparatus main body 12 (see FIG. 1), the fixing device 40 can be a unit that is detachable from the image apparatus main body 12. The upper wall portion 82a of the frame 82 forms a part of the conveyance path of the sheet that has passed through the separation claw 78, and the sheet that has passed through the upper wall portion 82a is discharged by the discharge roll 26 (see FIG. 1). It is discharged to the part 16 (see FIG. 1).

Next, the operation of the above embodiment will be described.
The image carrier 28 is uniformly charged by the charging device 30, and the charged image carrier 28 is irradiated with light emitted from the optical writing device 32 based on the image signal to form a latent image. Light from the optical writing device 32 passes through the process cartridge 46. The latent image of the image carrier 28 formed by the optical writing device 32 is visualized by the toner of the developing device 34.

  On the other hand, one of the sheet feeding devices 18 is selected based on a size signal or the like, and the sheet stored in one of the sheet storage units 20 is picked up by the pip-up roll 60 and conveyed to the registration roll 24 by the feed roll 61. When the leading edge of the sheet reaches the registration roll 24, the sheet is temporarily stopped by the registration roll 24, and is guided to the transfer section formed by the transfer device 36 and the image carrier 28 at a timing, and transferred by the transfer section. The developer image on the image carrier 28 is transferred to the sheet by the device 36. Then, the sheet on which the developer image has been transferred is sent to the fixing device 40.

  When the sheet reaches the fixing device 40, first, the leading end of the sheet is held in the nip N1, and the sheet with the leading end held is rotated by the heating roll 72 and the first roll 74. It is conveyed in the direction of the second nip N2. At this time, until the sheet leading end reaches the second nip N2, the sheet leading end receives a downward force, that is, a force in the direction of the heating roll 72 due to its own weight. Therefore, it is likely to be attached to the heating roll 72 and is conveyed to the second nip N2 in this state.

  Until the leading edge of the sheet reaches the nip N2, even if the leading edge of the sheet is not attached to the heating roll 72 but is lifted from the heating roll 72, the leading edge of the sheet remains the guide member 80. Guided by Therefore, the sheet front end portion remains in the vicinity of the heating roll 72. If the sheet tip is attached to the heating roll 72, it receives heat conduction from the heating roll 72, and if it is lifted from the heating roll 72, it receives heat radiation from the heating roll 72, and nips from the nip N1. It is heated while being conveyed to N2.

  As described above, when the leading edge of the sheet reaches the nip N2, the leading edge of the sheet is gripped by the nip N2. After the leading end of the sheet is gripped by the nip N2, the sheet is held under a certain tension from the first roll 74 and the second roll 76. It is difficult to be in a state of being lifted from 72, and the state of being attached to the heating roll 72 is easily maintained. While maintaining this state, the sheet is conveyed in a region between the first nip N1 and the second nip N2, and is heated by the heating roll 72 during this period.

  After the trailing edge of the sheet passes through the first nip N1, the sheet is held only by the nip N2. In this state, even if the rear end of the sheet is lifted from the heating roll 72, the rear end is guided by the guide member 80 and remains in the vicinity of the heating roll 72.

  In this way, the sheet on which the developer image has been fixed by being conveyed while being conveyed in the area between the nip N1 and the nip N2 is separated from the heating roll 72 by the separation claw 78, and is then placed on the frame 82. It is discharged to the discharge portion 16 by the discharge roll 26 through the wall portion 82a.

  In this embodiment, the heating roll 72 is a driving roll, and the first roll 74 and the second roll 76 are driven rolls that follow the heating roll 72. Instead, the first roll 74 is driven. As the roll, the heating roll 72 and the second roll 76 may be driven rolls that follow the first roll 74. Alternatively, the second roll 76 may be a driving roll, and the heating roll 72 and the first roll 74 may be driven rolls that follow the second roll 76.

  Further, both the first roll 74 and the second roll 76 may be drive rolls that are independently rotationally driven. In this case, the heating roll 72 may be a driven roll that is driven by either the first roll 74 or the first roll 76, or may be a driving roll that is independently driven to rotate.

  Further, in this embodiment, the peripheral speed of the first roll 74 and the peripheral speed of the second roll 76 are set equal, but the peripheral speed of the first roll 74 and the peripheral speed of the second roll 76 are May be different values. For example, the peripheral speed of the second roll 76 can be made faster than the peripheral speed of the first roll 74. In order to make the peripheral speed of the second roll 76 faster than the peripheral speed of the first roll 74, the first roll 74 and the second roll 76 are driven independently as described above. It can be a roll. Further, the angular velocity of the first roll 74 and the second roll 76 may be the same, and the diameter of the second roll 76 may be larger than the diameter of the first roll 74.

  When the peripheral speed of the second roll 76 is made larger than the peripheral speed of the first roll 74 in this way, the sheet is pulled in the conveyance direction by the second roll 76, and the first nip N1 and the second roll 76 Between the nip N2 and the nip N2.

  As described above, the present invention can be used in a fixing device that fixes a developer image on a sheet and an image forming apparatus having the fixing device.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Image forming means 28 Image carrier 30 Charging apparatus 34 Developing apparatus 36 Transfer apparatus 40 Fixing apparatus 70 Heat source 72 Heating roll 72a Cylindrical member 74 First roll 76 Second roll 78 Separation claw 80 Guide member 80a First groove 80b Second groove 82 Frame 82a Upper wall 83 Support member

Claims (3)

A heating roll;
A first roll that contacts the heating roll to form a first nip;
A second roll that forms a second nip in contact with the heating roll;
A guide means for guiding the conveyed sheet;
Have
The central axis of the first roll and the central axis of the second roll are located above the central axis of the heating roll in the direction of gravity, and convey the sheet from the first nip to the second nip. While heating ,
The guide means is provided with a first groove formed along the outer shape of the first roll and a second groove formed along the outer shape of the second roll. Fixing device. Support means for movably supporting the guide means between an open state retracted from the first roll and the second roll and a closed state close to the first roll and the second roll. The fixing device according to claim 1, further comprising: a fixing device; An image forming apparatus comprising the fixing device according to claim 1 .

Images