JP4596365B2 - 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 this type of fixing device, there is known a technique for fixing a developer image on a sheet by having a heating roll and conveying the sheet on which the developer image is formed with the heating roll while heating. Reference 1).

JP 2001-356625 A

However, the conventional technique has a problem that the sheet may not be satisfactorily heated by the heating roll without being in good contact with the surface of the heating roll. Further, the conventional technique has a problem that the sheet may not be peeled off well from the heating roll after fixing and sheet conveyance failure such as sheet clogging may occur.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to provide a fixing device in which heating of a sheet is favorably performed and a sheet after fixing is favorably peeled from a heating roll.

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 first roll that contacts the heating roll. A second roll that forms a nip of 2 and guide means for guiding the conveyed sheet, and the heating roll has at least a surface harder than the surface of the first roll, and the second roll The first groove is softer than the surface of the first roll and is heated while conveying the sheet from the first nip to the second nip , and is formed in the guide means along the outer shape of the first roll. And a second groove formed along the outer shape of the second roll . Accordingly, the first roll softer than the heating roll is deformed at the first nip, and the sheet is conveyed while being pressed against the heating roll at the first nip by being conveyed by the deformed first roll. Therefore, the sheet is conveyed in a state in which the sheet is in good contact with the heating roll. In addition, the heating roll softer than the second roll is deformed in the second nip, and the sheet is conveyed in the direction away from the heating roll in the second nip by being conveyed by the deformed superheating roll. Therefore, the sheet is favorably peeled from the heating roll. 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. It has the support means to support to. 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 the sheet is heated well and the sheet after fixing is favorably peeled from the heating roll.

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 A feed roll 61 that conveys the sheet picked up by the roll 60 and a retard roll 62 that is used as separating means 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. In addition, the retard roll 62 can use a roll-shaped thing as another embodiment instead of the plate-shaped thing shown in figure.

  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.

2 and 3, a fixing device 40 according to an embodiment of the present invention is shown.
The fixing device 40 includes a heating roll 72, a first roll 74 that contacts the heating roll 72 to form a first nip N1, and a second roll that contacts the heating roll 72 and forms a second nip N2. , A separation sheet guide member 78 for guiding a sheet separated from the heating roll 72, and at least a position close to the heating roll 72 and a position from the first nip N1 to the second nip N2. The guide member 80 used as the guide means is provided, and a frame 82 on which a part or all of each member constituting the fixing device 40 is mounted.

  The heating roll 72 includes, for example, a cylindrical tubular member 72a made of a metal tube such as aluminum, a heat source 70, and an outer peripheral layer 72b provided on the outer periphery of the tubular member 72a. The heat source 70 includes a halogen heater. The cylindrical member 72a is internally provided over substantially the entire area of the heating roll 72 in the axial direction, and heats the cylindrical member 72a and the outer peripheral layer 72b.

The outer peripheral layer 72b is a heat-resistant layer having heat resistance, and is an elastic body layer made of an elastic body that is elastically deformed when the second roll 76 is in pressure contact, and has a surface hardness measured by the Asker C method of 50. It is 55 degrees which is a value within the range of 60 degrees to 60 degrees. The outer peripheral layer 72b is made of silicone rubber and PFA (perfluoroalkyl vinyl ether copolymer resin) which is a fluororesin that is applied to the surface of the silicone rubber and makes it difficult to fix the sheet. Instead of applying PFA, for example, other fluororesins such as PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene hexafluoropropylene polymer resin), or silicone resin can be applied. However, PFA is optimal because of its good workability.

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.

  The first roll 74 is provided so as to be in contact with the outer periphery of the heating roll 72. For example, the first roll 74 is pressed against the heating roll 72 by a biasing means (not shown) such as a spring and the nip N 1 between the heating roll 72. And is rotatably supported by support means (not shown) such as a bearing. 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. No special drive transmission means is provided, and a configuration is adopted in which drive is transmitted to the first roll by the frictional force generated between the outer peripheral surface of the heating roll 72 and the outer peripheral surface of the first roll 74. Also good.

The first roll 74 includes a shaft 74a made of metal and an outer peripheral layer 74b provided on the outer periphery of the shaft 74a. The outer peripheral layer 74b is an elastic layer that is elastically deformed by being pressed against the heating roll 72, and has a surface hardness measured by the Asker C method of 45 degrees that is a value within a range of 30 degrees to 50 degrees. Become. Instead of the silicone sponge, other foamed sponge or silicone rubber may be used.

  The second roll 76 is brought into contact with 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 comes into contact, and forms a nip N2 with the heating roll 72. To do. The second roll 76 is supported by support means (not shown) including a bearing or the like, and is a driven roll that rotates as the heating roll 72 rotates, like the first roll 74. The 2nd roll 72 consists of metals, such as stainless steel, and the surface hardness measured by Asker C method is 70 degree | times which is a value 60 degree | times or more.

  As described above, the heating roll 72 has a surface hardness measured by the Asker C method of 55 degrees, the first roll 74 has a surface hardness measured by the Asker C method of 45 degrees, and the second roll 76 has an Asker C The surface hardness measured by the C method is 70, and at least the surface of the heating roll 72 is harder than the surface of the first roll 74 and softer than the surface of the second roll 76. For this reason, the first roll 74 softer than the heating roll 72 is elastically deformed at the first nip N1, and is conveyed by the elastically deformed first roll 74, thereby passing through the first nip N1. The sheet is conveyed while being pressed against the heating roll 72 in the direction of arrow A shown in FIG. Further, the heating roll 72 softer than the second roll 76 is elastically deformed in the second nip N2, and the sheet discharged from the second nip N2 is conveyed by the elastically deformed heating roll 72. The sheet is conveyed in the direction of arrow B shown in FIG. 3 in the direction away from the heating roll 72, and the sheet is favorably peeled from the heating roll 72.

  Further, as described above, the hardness of the surface of the heating roll 72 is in the range of 50 ° to 60 ° at Asker C, and the hardness of the surface of the first roll 74 is in the range of 30 ° to 50 ° at Asker C. Since the hardness of the second roll 76 is 60 ° or more at Asker C, the difference between the hardness of the surface of the heating roll 72 and the hardness of the surface of the first roll 74 and the surface of the second roll 76 The difference between the hardness and the hardness of the surface of the heating roll 72 can be made sufficiently large.

  Further, as described above, the heating roll 72 has a surface hardness measured by the Asker C method of 55 degrees, the first roll 74 has a surface hardness measured by the Asker C method of 45 degrees, and the second roll 76. The surface hardness measured by the Asker C method is 70 degrees, the difference between the Asker C hardness on the surface of the heating roll 72 and the Asker C hardness on the surface of the first roll 74 is 10 ° or more, and the second roll 76 The difference between the hardness due to Asker C on the surface and the Asker C hardness on the surface of the heating roll 72 is 10 ° or more. For this reason, the first roll 74 is sufficiently deformed at the first nip N1, and the sheet comes into contact with the heating roll 72 more favorably at the first nip N1. Further, the heating roll 72 is sufficiently deformed at the second nip N2, and the sheet is more easily peeled off from the heating roll at the second nip N2.

  Further, 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 first roll 74, the second roll 76, and the heating roll 72. The peripheral speeds are 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. Thereby, it is possible to arrange the two rolls of the first roll 74 and the second roll 76 around the heating roll 72 while maintaining the state in contact with the heating roll 72. 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.

  Moreover, although the diameter R1 of the 1st roll 74 and the diameter R2 of the 2nd roll 76 are substantially the same diameter, the diameter R1 and the diameter R2 can also be set to different values. The diameter R1 may 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 sheet guide member 78 is a plate-like member that is positioned at a position where one end is opposed to the second nip N2 without being in contact with the heating roll 72, and the other end is mounted on a frame 82 described later. Then, the sheet separated from the heating roll 72 is guided in the direction of the discharge roll 26 (see FIG. 1). The separation sheet guide member 78 has a function of guiding the sheet separated from the heating roll 72, but does not have a function of separating the sheet from the heating roll 72. A separation claw having a function of separating the sheet from the heating roll 72 may be provided together with the separation sheet guide member 78 or instead of the separation sheet guide member 78.

  The guide member 80 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.

  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 a shaft 83 used as a supporting means for supporting. The shaft 83 rotatably supports the guide member 80 with the vicinity of the rear end portion in the sheet conveying direction of the guide member 80 as a fulcrum. By providing the shaft 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 is performed. It becomes easy. In FIG. 2, the guide member 80 in the closed state is shown.

  The heating roll 72, the first roll 74, the second roll 76, and the separation sheet guide member 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 forming 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 sheet guide member 78, and the sheet that has passed through the upper wall portion 82a is discharged by the discharge roll 26 (see FIG. 1). , And discharged to the discharge unit 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, since the first roll 74 is elastically deformed at the nip N1, the sheet is pressed against the heating roll 72, and thus the sheet tends to adhere to the heating roll 72. In addition, until the sheet leading end reaches the second nip N2, the sheet leading end receives a force in the downward direction, that is, in the direction of the heating roll 72 due to its own weight. Also from this, the sheet tends to be attached to the heating roll 72.

  Until the leading end of the sheet reaches the nip N2, even if the leading end of the sheet is not attached to the heating roll 72 but is lifted from the heating roll 72, the leading end of the sheet is not guided. Guided by member 80. 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.

  When the sheet leading end reaches the nip N2, the sheet leading end 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.

  In the nip N2, the heating roll 72 is elastically deformed by the second roll 76 being pressed, and the sheet is conveyed in a direction away from the heating roll 72 by the elastically deformed heating roll 72, whereby the sheet is It is peeled off from the heating roll 72.

  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 manner, the developer image is fixed by being conveyed while being conveyed in the area between the nip N1 and the nip N2, and the sheet peeled from the heating roll 72 at the nip N2 is guided to the separation sheet guide member 78. Then, it is discharged to the discharge portion 16 by the discharge roll 26 through the upper wall portion 82a of the frame 82.

  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 showing 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. FIG. 3 is an explanatory view showing, in an enlarged manner, main portions of 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 72b Outer peripheral layer 74 First roll 74a Shaft 74b Outer peripheral layer 76 Second Roll 78 separation sheet guide member 80 guide member 80a first groove 80b second groove 82 frame 82a upper wall 83 shaft

Claims (3)

A heating roll;
A first roll that contacts the heating roll to form a first nip;
A second roll that abuts against the first heating roll to form a second nip ;
A guide means for guiding the conveyed sheet;
Have
Wherein the heating roll is harder than at least the surface of said first roll surface, and softer than the surface of the second roll, and heated while conveying the sheet from said first nip to said second nip ,
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